isis volume 57 issue 4 1966 [doi 10.2307%2f228517] richard c. dales and robert grosseteste -- the...

The Text of Robert Grosseteste's Questio de fluxu et refluxu maris with an EnglishTranslationAuthor(s): Richard C. Dales and Robert GrossetesteSource: Isis, Vol. 57, No. 4 (Winter, 1966), pp. 455-474Published by: The University of Chicago Press on behalf of The History of Science SocietyStable URL: http://www.jstor.org/stable/228517 .Accessed: 08/05/2014 23:48

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DOCUMENTS AND TRANSLATIONS

The Text of Robert Grosseteste's

Questio defluxu et reflux maris with an English Translation

By Richard C. Dales *

A remarkable short study of the tides, probably by Robert Grosseteste, was first discovered by Father Franz Pelster in Assisi.1 In 1940 S. Harrison Thomson noted three other manuscripts of the same treatise,2 and in 1952 Ezio Franceschini published the text of this work on the basis of three of the four manuscripts.3 His edition unfortunately contains several impossible and many questionable readings, it is carelessly printed, and its apparatus is unnecessarily encumbered by the notation of all the variants in MS V (see the discussion of this manuscript below). Furthermore, Grosseteste's authorship has been challenged by several scholars of considerable emi- nence,4 and Professor Franceschini has himself conceded that Grosseteste was probably not the author. There is therefore a clear need for a more thorough edition and a more reliable text, and it is that which I hope to provide here.

Of the four manuscripts of this treatise, the earliest is Assisi, Biblioteca Comunale, MS 138, folios 261D-262B (= A). Copied for use of St. Bona- venture probably from an English exemplar before the year 1250,5 it contains the ascription " Questio de fluxu et refluxu maris a magistro R.[? or A. or N.] exon. in scolis suis determinata," and in the margin opposite

* University of Southern California. 1F. Pelster, "Zwei unbekannte philosoph-

ischen Tractate des Robert Grosseteste," Scholastik, 1926, 1:572-573.

2 S. H. Thomson, The Writings of Robert Grosseteste, Bishop of Lincoln, 1235-1253 (Cambridge: Cambridge Univ. Press, 1940), p. 89.

3 E. Franceschini, "Un inedito de Roberto Grossatesta: La ' Questio de accessu et recessu maris,'" Revista di Filosofia Neoscolastica, 1952, 44:11-21.

Isis, 1966, VOL. 57, 4, No. 190.

4 See the summary of their arguments in D. A. Callus (ed.), Robert Grosseteste, Scholar and Bishop (Oxford: Clarendon Press, 1955), p. 22. Father Callus concludes that "certainly it is not by Grosseteste."

5 F.-M. Henquinet, O.F.M., " Un recueil de questions annote par S. Bonaventure," Ar- chivum Franciscanum Historicum, 1932, 25: 553-555. See also Thomson, loc. cit., who dates it c. 1225 on paleographical grounds but con- cedes that this may be stretched to mean almost 1250.

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RICHARD C. DALES

the last line of the treatise and just before Grosseteste's De subsistencia rei 6 the words "Magister R. Grosseteste." Its early date gives it particular authority in matters of spelling, word order, use of numerals and title, and whenever there is no more reason to adopt one reading than another, we accept the version of A. Its value is somewhat vitiated, however, by scribal carelessness. It omits three important sections by homoioteleuton (I, 92-93; II, 17, and 43-45 7), lacks key words (such as non-I, 110; III, 16) in critical places, or reverses accessio and recessio (I, 65-66). Valuable as this manuscript is, we are indeed fortunate to have other versions.

Clearly in the same tradition is Vatican, Barb. lat., MS 165 (== V), written in a German hand and dated 1288 in a colophon on folio 402D. The De fluxu appears on folios 402D-403B and is ascribed to Boethius, but it is followed by Grosseteste's De iride, also ascribed to Boethius. This version is actually a paraphrase of the treatise and breaks off about two-thirds of the way through it. It not only omits many words and phrases but also frequently changes the structure of sentences so that the cases of the nouns and the number and voice of the verbs are different. There seems to be no point in noting all these variants in the apparatus, and so they shall be omitted. However, this abridgement is quite early and seems to have been based on a good text. At times, V gives us the only correct reading of a passage, and whenever it provides a likely or significant reading, this will be noted.

Next in time, and probably the best version all in all, is that of Florence, Biblioteca Marucelliana, MS C. 163, folios 18A-19c (= F). This is a paper codex, written in a beautiful prehumanistic Italian book hand of around 1400. It contains one of the most important extant collections of Grosse- teste's theological and philosophical works and Robert Holcot's Commentary on the Sentences. Although it contains some occasional slips, its text is generally excellent and in several places preserves important sections of the work which would otherwise be lost. It attributes the work to Grosse- teste (Lyconiensis).

Closely related to F, and also ascribing the De fluxu to Grosseteste, is another extremely important collection of Grosseteste's philosophical and theological works: Prague, National Museum, MS XII. E. 5 (= P).8 It is written in a tiny, badly formed, and highly abbreviated Bohemian hand of around 1450,9 and is extremely difficult to read. It agrees with F in a majority of cases, not only in the variants noted in the apparatus, but also in word order. The agreement is not consistent, however, and P contains several unique readings. Although its text is not of such consistently high quality as F, it occasionally provides us with a superior reading. The De fluxu is on folios 41C-42A.

The problem of authorship is probably ultimately insoluble, but the

6 Father Callus had this treatise nearly ready the Latin text presented later. for publication at the time of his death in 8 For a full account of this codex, see F. M. June 1965. It is being seen through the press Bartos, Soupis rukopisii narodniho musea v by R. W. Hunt. Praze (Prague, 1926), Vol. 2, p. 232.

7These section and line numbers refer to 9 It is so dated by Thomson, loc. cit.

456


ROBERT GROSSETESTE'S QUESTIO DE FLUXU ET REFLUXU MARIS 457

evidence inclines heavily toward Grosseteste. I have presented this evidence in detail in a previous article 10 and offer merely a summary here. First are the ascriptions. In all four manuscripts, the De fluxu appears among a group of Grosseteste's authenticated writings, and in two of these (P and F) it is definitely ascribed to him. The question as to his authorship arises from the difficulty in deciphering the initial in the ascription of A. But since the internal evidence strongly indicates that Grosseteste was the author, we should probably consider this troublesome and unusually formed initial as the result of scribal uncertainty. Secondly, the De fluxu has certain features which are characteristic of Grosseteste: the Light Metaphysics, the predilection for mathematics in investigations of physical phenomena, the methods of resolution and composition and of experimental verification and falsification,11 and the use of several experiments of which Grosseteste was particularly fond and which he used in several other scientific works (see below, notes d, e, f). Third is the use of a concept related to the Light Metaphysics, that light rays are incorporated in a dense medium and produce heat by scattering the parts of that medium when the rays are reflected back upon themselves.l2 And finally there are Grosseteste's similar remarks on the tides in several of his other works, namely De impressionibus aeris, Commentarius in libros posteriorum Aristotelis, and most important his De natura locorum, where he resumes and answers a question left un- answered in De fluxu - how the moon can influence the tides when it is on the opposite side of the earth (see below, notes a, b, c). If Grosseteste was not in fact the author, he is at least the most likely candidate of whom we have knowledge.

The tides had been the object of scientific investigation at least since the time of Aristotle, and a smattering of the knowledge of the great Hellenistic investigators had survived in the Latin handbook tradition.13 In addition, Bede had made some very important observations on tidal phenomena, including their relationship to the motion of the moon and the principle of the establishment of port, in his De temporum ratione.l4 During the

0 R. C. Dales, "The Authorship of the Questio de fluxu et refluxu maris Attributed to Robert Grosseteste," Speculum, 1962, 37: 582-588.

1 For a brilliant analysis and description of Grosseteste's scientific method, see A. C. Crombie, Robert Grosseteste and the Origin of Experimental Science, 1100-1700 (Oxford: Clarendon Press, 1953).

12 On the development of this concept in Grosseteste's scientific works and its usefulness in dating his works, see R. C. Dales, " Robert Grosseteste's Scientific Works," Isis, 1961, 52: 381-402. I should like here to acknowledge and correct an error I made in that article. On p. 388, n. 16, I wrote: " If this means what it seems to - that ships draw less water at high

tide than at low tide--it (and the following assertion that water is hotter at high tide) is an example of flagrantly inaccurate observa- tion." Miss E. G. R. Taylor has correctly pointed out (" Robert Grosseteste as an Ob- server," Isis, 1964, 55:342) that in the estuary of a river the phenomena would be as Grosse- teste described them. See below, I, 62-69.

13 A recent publication, W. H. Stahl, Roman Science (Madison: Univ. Wisconsin Press, 1962), traces in detail the transmission of Greek science through the handbooks and encyclopedias.

14 Bede, De temporum ratione, cap. XXIX, "De concordia maris et lunae," printed in J. P. Migne, Patrologia Latina, Vol. 90 (Paris, 1862), cols. 422-426.


RICHARD C. DALES

twelfth century, the Spanish Moslem al-Bitruji (Alpetragius),15 as a conse- quence of his " Aristotelian " astronomy, proposed a new explanation of the tides (summarized and refuted in De fluxu) which Michael Scot translated into Latin about 1220; Gerald of Wales, an acquaintance of Grosseteste, compiled some important data on tidal phenomena on the opposite coasts of England and Ireland, and although he noted their relationship to the motion of the moon, he resorted to the Maelstrom to explain them; 16 and the works of Ptolemy and other Greek and Arabic writers had been translated into Latin. By the early thirteenth century, then, there was a long tradition of tidal investigation accessible to scientists, a body of reliable data, and several proposed explanations. The author of De fluxu was clearly cognizant of this tradition, but instead of choosing among already existing alternatives, he undertook an original investigation using new methods and techniques.

In form De fluxu is a scholastic questio of an early and free type often used by Grosseteste, not of the later, highly formalized type such as appeared after the middle of the thirteenth century. If it was indeed written by Grosseteste and was "in scolis suis determinata," as the note in MS A asserts, then it was written probably before 1229, when he became lecturer to the Oxford Franciscans, and definitely before 1235, when he became Bishop of Lincoln. Internal evidence enables us to date it still more precisely (still assuming that Grosseteste was the author) as within a year or two of 1227.17

In the text which follows, the spelling of the codices has been retained and in case of variation, that of A has been adopted. Differences in spelling are not noted in the apparatus, nor are minor or inconsequential variants, inversions of word order, or obvious scribal slips. In the case of uncertain readings the scribe is given the benefit of the doubt if what he has written may reasonably be interpreted as the correct reading. The designation lectio incerta is used only in those places where there is reasonable doubt as to what the scribe intended. With these exceptions, the apparatus gives a nearly complete account of the texts of A, F, and P; as we have mentioned above, the readings of V are included only when they seem significant. The beginning of each column in each manuscript is indicated in square brackets after the first word of that column.

15 See F. J. Carmody, Arabic Astronomical from Thales to Kepler, New York: Dover, and Astrological Science in Latin Translation 1953), pp. 264-267 in original edition. (Berkeley: Univ. California Press, 1956), pp. 16 In Geraldi Cambrensis Topographica Hi- 165-166; G. Sarton, Introduction to the History bernica, "De aequoreis fluxibus in Hibernia of Science (Baltimore: Published for the et in Britannia," dist. II, cap. ii, and " Quod Carnegie Inst. by Williams & Wilkins, 1931), Luna tam liquores moderatur quam humores," Vol. 2, Pt. 1, pp. 400-401; J. L. E. Dreyer, dist. II, cap. iii, Opera omnia, Vol. 5, ed. J. F. History of the Planetary Systems from Thales Dimock (London, 1867), pp. 77-78. to Kepler (Cambridge: Cambridge Univ. Press, 17 Dales, " Robert Grosseteste's Scientific 1906; reprinted as A History of Astronomy Works," op. cit., p. 391.

458



Questio de fluxu et refluxu maris I

Intendentes de accessione et recessione maris, intendamus 1 primo de causa materiali que 2 duplex 3 est causa, videlicet 4 communis et propria.

Communis est hec: Sic ordinate sunt spere 4 elementorum quod terra est in medio et ignis in ultimo locorum, aqua et aer in locis mediis inter hec. Per condensationem 5 [P 41D] et rarefactionem sunt ista apta ut moveantur. Sed aqua et aer magis communicant has 6 differentias quam ignis et terra; ergo magis apta ut moveantur. Probatio minoris: Condensatio

10 est motus partium materie ad medium et rarefactio est motus partium materie ad ultimum. Quod est ergo penitus7 in medio non est ulterius 8 condensabile,9 ut terra; et quod est in ultimo non est ulterius rarefactibile, ut ignis. Que autem in locis mediis sunt inter medium et ultimum rarefieri et condensari possunt,10 ut sunt aqua et aer.

Propria: In aqua et in aere, cum ipsa 11 moveantur maxime in eis, est omnis motus generabilis et corruptibilis. De motibus aeris omittamus et 12 [F 18B] loquamur de motibus 13 aque.

Et vertitur hec questio circa tria. Prima pars est de 20 causa materiali et efficiente istorum motuum. Secunda pars

est de causis signantibus augmentationem et diminutionem in accessione. Tertia pars est de divisione 14 marium quibus accidit hoc vel non accidit 15 vel non videtur accidere.16

Disputantes ergo 17 ad partem primam, intendamus primo de causa efficiente, et necesse est quod hec causa efficiens sit virtus celi vel virtus stelle in celo. Non enim movetur elementum ex se vel elementum ex elemento, sed omnem motum elementorum oportet 18 reducere ad causam efficientem que sit species immaterialis.19

30 Et ad hoc dicit Alpetragius quod ex virtute celi ultimi quod est supra speram stellarum fixarum moventur omnes spere inferiores ab oriente in occidentem et ultima 20 spera aque. Sed unaqueque spera quanto est 21 inferior tanto minus recipit de virtute ultimi, cum hec virtus sit virtus corporis 22 et propterea 23 est 24 ex distantia recipiens diminutionem. Terra autem propter maximam sui 25 distantiam a spera ultima et propter sui grossitatem omnino manet immobilis. Movetur ergo aqua 26 maris per virtutem celi ultimi ab oriente in occidentem et ex hoc dicit accidere 27 conculcationem 28 aquarum et accessionem.

1A intendimus; V et. 2A quedam; FP quare. s A duplex deest. 4A causa videlicet deest; F videlicet deest. 5A autem seq. 6F has deest; V istas. 7A penitus deest. 8 A magis. 9 A aut ultra condensabilem seq.; V ultra

condensabile. 0 PV possunt deest.

11A omni et ipse. 12 A ut. 13 AV motu. 14 A diminutione.

15 F hoc seq. 16 FP vel . . . accidere deest. 17 A ergo deest. 18 FP est. 19 FP materialis; V in materialem. 20 FP ultra. 21 A est deest. 22 FP in corpore. 23 AF propria; V propter quod. 24 APV est deest. 25 FP sui deest. 26 p Motus autem aque. 27 A accidit. 28 A coelevationem seq.


RICHARD C. DALES

40 Sed accedit ad29 pristinum locum propter sui ponderositatem et cum perfecta fuerit reversio incipit iterum moveri et ascendere 30 quousque patitur sua ponderositas et tunc consequenter refluit. Et iste due accessiones et recessiones optinent tempus plus die uno cum nocte sua.

Quod hoc 31 sit falsum sic patet: In celo ultimo partes que velocissime moventur sunt partes existentes in equinoctiali circulo sub quo edirecto 32 in superficie terre est mare magnum quod appellatur occeanus 33 circumdans circulariter; et hoc est principium omnium marium. Si ergo in 34 una parte celi esset

50 virtus motiva et non in alia, in ortu huius partis sequeretur maris motus in parte 35 una et non in parte 36 alia. Si ergo moveretur una pars maris 37 et non alia, resisteret una pars alii et necesse esset unam partem elevari super aliam et locum maiorem occupare. Sed cum fuerit hoc mare circulare 38 et in omni parte equinoctialis circuli 39 est virtus motiva equaliter, ergo omnes partes maris existentes edirecto 40 singularium partium equinoctialis movebuntur equaliter in partem eandem. Ergo non erit resistentia in parte aliqua ad motum alterius partis nec invenietur 41 causa quare oportet 42 aquam locum

60 maiorem occupare. Item si hoc modo moveretur mare, moveretur localiter

tantum43 ex tali causa. Sed percipimus experimento quod accessio et recessio maris est ex quadam rarefactione et condensatione eius. Naves enim 44 in mari magis elevantur supra mare in tempore accessionis 45 quam in tempore 46 recessionis 47 et hoc est quia recessio fit per subtiliationes partium et accessio 48 per condensationem.49 Item 50 in tempore accessionis invenitur aqua calidior quam in tempore recessionis et hoc non est nisi propter minorem partium subtilitatem.50 Contra racionem 51

70 Alpetragii hec rationes 52 et experimenta sufficiant. Quod [V 403A] non ymago aliqua 53 stellarum [F 18C]

fixarum vel planeta aliquis 54 sit causa 55 huius motus preter lunam videtur per hoc 56 quod nullius corporis celestis 57 sequitur motum motus maris preter quam motum lune; ipsi autem omnino proportionatur,58 ut inferius patebit. Rationes 59 astronomie similiter inducunt nos ad hoc: Cum enim sint duo 60 luminaria magna, sol et luna; sol autem habet significationem superl6

29 A accidat. 30-FPV accedere. 31 A ergo. 32 FP directe. 33 A occeanum. 34 P in deest. 35 A autem seq. 36 p parte deest. 37 FPV maris deest. 38 FP occeanus circulariter. 39 FP equinoctialis circuli deest. 40 FP ex directo. 41 P inveniet. 42FP contingit; V oporteat. 43FP tantum deest. 44 FP qua naves. 45 A recessionis.

46 FP in tempore deest. 47 A accessionis. 48 A recessio. 49 F condensationes partium. 50P Item . . . subtilitatem deest. 51 A Contra rationem deest. 52 A et deest. 53A alia. 54A aliqua; P aliquid. 55FP causa deest. 56 AV probari; F preter hoc. 57 F celestis deest; P corporis celestis deest. 58 AF proportionantur; V proportionaliter

(vide infra, II, 13, 45-47). 59 FP vero seq. 60A due. 61A V super.

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ROBERT GROSSETESTE'S QUESTIO DE FLUXU ET REFLUXU MARIS

temperamentum aeris principaliter tunc et luna habebit principaliter 62 significationem super temperamentum aque a cum in

80 hiis 63 duabus speris fiat generatio et corruptio omnium ani- mantium 64 et hec duo luminaria sint principalia principia omnis generationis et corruptionis. Item experimento scimus quod luna inter omnes 65 substantias celestes 66 maximam 67 significationem habet super humida et frigida. Unde dicuntur68 quidam 69 lunatici quia 70 in defectu lune patiuntur diminucionem 71 cerebri, cum cerebrum sit substantia frigida et humida. Hiis ergo rationibus sufficit quod luna sit causa sufficiens et 72 efficiens accessionis et recessionis maris.73

Sed quomodo 74 sit causa nunc est 75 inspiciendum. Cum 90 oritur76 luna in orizonte 77 alicuius maris tunc primo infundit 78

62 FP principaliter deest. a Cf. Roberti Grosseteste Commentarius in

libros posteriorum Aristotelis (ed. Venice, 1494, fols. 29D-30A): " Quedam vero que sunt sub uno analogo sic se habent adinvicem quod alterum est sub reliquo sicut causatum sub causa, sicut nili fluxus et mensis variatio secundum quatuor anni tempora, et decre- mentum et incrementum lune. Hec tria con- veniunt in uno analogo quod est non permanentia in statu uno. Luna namque continue crescit aut deficit lumine et hac sui permu- tatione permutat qualitates temporis in quatuor quartis mensis. Ipsa enim movet in omni mense quatuor anni tempora quia efficit primam quartam mensis calidam humidam lumine suo cre- scente, secundam calidam siccam per comple- mentum sui luminis, tertiam quartam efficit siccam et frigidam lumine deficiente a comple- mento, ultimam quartam frigidam et humidam defectu sui luminis; et ita in fine mensis est humidior mensis, non tamen frigidior, sed est accedens ad calorem. Patet igitur quod tam in mense quam in luna est permutatio con- tinua et non permanentia in statu uno. Et permutatio in luna est causa permutationis in tempore mensurato. Causa vero permutationis in tempore est causa permutationis in naturis quatuor et in rebus mutabilibus participanti- bus quatuor naturis, sicut humiditas finitatis mensis est causa augmentationis humiditatis in rebus humidis. Dico etiam quod virtus lune est virtus humectans et virtute sua humectante humectat aerem et augmentat humidum in aquis et cum coniungitur soli vigoratur virtus eius calida per virtutem solis et virtus solis calida virtuti lune humectanti fortiter admix- tanencio [sic!] humore augmentato cum calore faciunt aquas rarefieri et inturgescere, unde humecto in fine mensis cum luna coniungitur soli plus solito intumescunt aque tam salse quam dulces, licet non sic sit manifestum in dulcibus sicut in salsis; et propter hoc in fine mensis sunt fluxus marium maiores et quod- dam mare est quod non fluit nisi in fine mensis et in medio mensis. In medio namque mensis plenitudo luminis eius quod recipit a sole con- fortat virtutem eius, licet hec confortatio et

vigoratio non sit tanta quanta est per coniunctionem corporalem. Itaque omnes aque in fine mensis plus inundant, sed inundatio earum plus apparet in quibusdam et in quibusdam minus propter alias concausas adi- unctas sicut accidit in nilo quod in fine mensis lunaris propinquioris equinoctio autum- nali plus abundant eius aque, quia nilus cadit in mare inter occidentem et septentrionem et ventus occidentalis fiat in regione illa a maio usque ad equinoctium autumnale et movens aquas maris secundum vias incessus sui movet etiam arenam et obstruit arena ostia nili, et hec obstructio et venti occidentales reluctatio faciunt aquas nili augmentari et inundare. Causa ergo vera et prima inundationis nili est vis lune humectans et rarefaciens aquas que vigorata per coniunctionem solis plus facit humecto in fine mensis cum luna deficit. Hec tamen causa non educit ex se suum effectum plene nisi cum concausis predictis, scilicet ob- structione ostiorum et venti occidentalis contra incessum nili reluctatione et he concause acci- dunt circa equinoctium autumnale. Unde virtus lune augmentans aquas in fine illius mensis plus manifestat operationem sue vir- tutis in aquis nili. Igitur proxima causa fluxus nili in fine predicti mensis est quia finis mensis est humidior. Finis autem mensis humidior est propter lune defectum et coniunctionem eius cum sole in ipso defectu."

63 FP hiis deest. 64 p generantium; V aliorum. 65 P speras et seq. 66 FP supercelestes. 67 F magnam. 68 A dicunt. 69 F quedam. 70 p quia deest. 71 FP defectum. 72A sufficiens et deest. 73A maris deest. 74 P oportet quodammodo. 75 A est deest; P discutiendum vel seq. 76 A oriatur. 77 AV oriente. 78FP effundit.

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radios luminares 79 in medio maris et fortiter imprimens 80 suam virtutem movet 81 hoc mare augeturque hec 82 motio quousque pervenerit.83 luna ad circulum meridionalem.82 Cum autem transierit circulum meridionalem minoratur virtus effectiva et recedit mare ad 84 canales proprios quousque pervenerit luna ad occidentem. Cum iterum transierit 85 ab occidente usque ad medium celi sub terra, augmentatur mare; et cum transierit a medio cell sub terra minuitur quousque veniat iterum ad ortum; et sic in 86 una revolutione lune ab ortu ad ortum perficiuntur due

100 accessiones maris in eodem loco super 87 cuius 88 orizontem [A 262A] est ortus lune.

Quare 89 autem sic dividantur accessiones et recessiones secundum 90 quattuor quartas huius 91 ratio difficilis est.89 De duabus enim quartis que sunt ab ortu usque ad medium celum et a medio celo usque ad occasum, quare hec accessioni conveniat, illa vero 92 recessioni, satis manifestum est ex dictis. Dum enim ascendit fortius imprimit suam virtutem quam cum descendit ad occasum. Sed de duabus quartis que sunt sub orizonte illius maris cum in eis luna existens non sit presens nec illuminans

110 mare illud. Cum corpora celestia93 non94 agant in inferiora nisi per sua lumina, dubium est quomodo possit esse principium motionis maris. Ad hoc respondent astronomi quod opposite quarte in celo effectus habent consimiles,95 sed utrum sit hoc restat querendum et maioris eget speculationis b

79 F lunaris; V luminosos. 0 FPV imprimit.

81 FP movetque. 82A hec . . . meridionalem deest. 83 Coni. Codd. pervenit. 84A ad deest. 85 A transierat. 86p in deest. 87 FP sub. 88 p vel super cuius seq. 89p Quare . . . est deest. 90 F super. 91 F hec. 92 AFP vero deest. 93 FP supercelestia. 94 A non deest. 95 P similes. b Cf. Roberti Grosseteste De natura locorum

(L. Baur, Die philosophischen Werke des Robert Grosseteste, Bischofs von Lincoln, in Beitrige zur Geschichte der Philosophie des Mittelalters, Bd. 9 [Miinster i. W.: Aschen- dorff, 1912], pp. 69-70): " Quia enim radii lunares orientes super mare alicuius regionis habent longiores lineas et pyramides et sunt minus recti et minus cadunt ad angulos aequales et minus reflectuntur in se et magis franguntur, ideo sunt debiliores, quam quando luna ascendit ad medium caeli. Tunc enim radii omnes habent breviores lineas, et pyramides rectiores et cadunt magis ad angulos aequales, et sunt magis perpendiculares et magis redeuntes in se et minus fracti, ut patet inquirenti; et ideo sunt fortioris operationis. Propter quod, quando luna oritur, radii eius propter debilitatem eorum non possunt nisi resolvere vapores a fundo terrae et aquae et

elevare infra corpus maris, et non possunt consumere eos neque ad aerem complete extrahere. Et ideo isti vapores expellunt aquas maris a locis suis, quoniam corpus sunt et non possunt esse simul cum partibus aquae. Et ideo generant ampullas in corpore maris et tumores, et ideo fluit tunc mare. Sed quando luna ascendit ad medium caeli, propter fortitudinem radiorum potest et vapores illos resolutos consumere et ad aerem extrahere et elevare. Et cum pervenit ad punctum meri- diei, iam complete consumpsit et extraxit, et quia cessante causa cessat effectus, ideo aquae maris tunc naturaliter recurrunt in locum suum ne fiat vacuum. - Sed quando est fluxus in una quarta mundi, est fluxus ibi in quarta opposita. Cuius summae difficultatis rationem multi astruere conantur per hoc, quod quartae mundi oppositae sunt eiusdem commixtionis, et ideo faciunt eosdem effectus. Sed ista ratio deficit tamen, quia falsa est, eo quod aliquae sunt imagines stellarum in una quarta et in alia, quoniam, quando planeta est super unam quartam mundi, tunc terra interponitur inter corpus eius et aliam quartam. Propterea, si hoc esset verum, peteretur principium. Quaeri- tur enim causa, quare sunt oppositae quartae eiusdem commixtionis et per consequens eiusdem effectus. Et ideo reflexio radiorum solvit istud, quoniam radii lunares multiplicantur ad caelum stellarum, quod est corpus densum. Ideoque per medium eius non possumus videre caelum, quod est valde luminosum, sicut dicit Alpetragius et Messalahe. Et alii radii reflexi cadunt in quartam oppositam ad angulos aequales."

462



Sicut 96 ergo tempus revolutionis lune ab ortu ad ortum excedit tempus diei et noctis, ita tempus duarum accessionum et duarum reversionum 97 diversarum et perfectarum excedit 98 [F 18D] tempus diei et noctis. Scito ergo per quot horas subsequatur vel 99 precedat 1 ortus 2 lune ortum 3 solis. Scitur 4

120 per quot horas subsequitur vel precedit 2 initium accessionis initium diei et qua una 5 lunatio continet XXIX 6 dies et aliquot minuta. In VII ergo diebus et quarta diei et aliquot minutis 7 distabit luna a sole secundum quartam circuli versus orientem; 8 unde 9 in tertio huius temporis cum fuerit sol in ortu erit luna in medio celi sub terra et erit tunc 10 principium recessionis, cum in 11 initio illius temporis fuerit principium accessionis. Hoc autem tempore duplicatio 12 erit cum fuerit sol in oriente 13 luna in occidente 14 et erit tunc principium accessionis. Si vero 15 ulterius distiterit16 a sole secundum

130 tres quartas cum fuerit sol in ortu erit luna in medio celi super terram et erit principium recessionis. Cum autem iterum 17 coniungitur 18 soli erit tunc simul in principio diei inicium accessionis. Et hoc est quod dicunt naute, quod si in initio 19 diei fuerit initium accessionis septem diebus completis erit in 20 inicio sequentia diei inicum 21 recessionis. Sed hec accessio et recessio in eisdem temporibus non apparent in litoribus maris eo quod distant 22 a medio maris ubi initium sumit 23 hec accessio et recessio. Et scias 24 quod in litoribus propinquioribus austro vel orienti citius fuerint 25 accessiones.

140 Et tantum 26 sufficiat de causa efficiente. Restat nunc de causa materiali propria, et est hoc:

Quod oportet 27 aquas congregari in loco profundo et lato in quibus aquis est multa materia vaporum et ventorum.28 Unde ascendens luna et imprimens suam virtutem generat in eis multos vapores et excitat ventos.c Aqua vero illa propter 29

96 P tunc. muntur. 97 FP recessionum. 24 A scias deest; V sciat. 98 P accedit. 25 FP fiunt; V sunt. 99 AV et. 26FP hec. 1 FP precedit. 27 P contingit. 2 A ortum; P ortus . . . precedit deest. 28 FP spumarum. 3 A ortum deest; F lectio incerta. e Cf. Roberti Grosseteste De impressionibus 4 F scietur. aeris (Baur, op. cit., pp. 48-49): "In operibus 5 F una deest. autem lunae est manifestum, ut patet in 6 FP 30; V XIX. fluxu et refluxu maris. Cum enim movetur 7F minutas; P minuta. luna ad augen sui deferentis, augetur fluxus 8 FP orizontem. maris; cum vero recedit ab auge, minuitur 9 P usque. fluxus eius, donec pervenerit ad oppositum 10 P tunc deest. augis. Et secundum astrologos luna est in 11 A in deest. auge sua in qualibet coniunctione cum sole 12 AF duplato. et similiter in qualibet praeventione vel op- 13 P orizonte. positione. Ideo fluit mare et refluit bis in 14 F occidentem. mense lunari. Nota, quod luna est causa fluxus 15 F tunc seq. maris; oriente enim luna congregantur undique 16 F disteterit; P distetetur. aquae maris et cumulantur et elevantur quasi 17 PV iterum deest. versus suam causam et originem; nec cessat 18 FP coniungetur. talis augmentatio, donec pervenerit luna ad 19 A huius seq.; V illius seq. lineam meridionalem. Quam cum transierit, 20 p in deest. minuitur tumor ille et fluunt aquae ad locum 21 P in initio. oppositum et generatur ibi tumor consimilis. 22 A distent. Et haec est causa, quare apparent duo fluxus 23 AV fuerit; P fiunt; F sumit cor. ex sum- in die naturali. Unde ubicunque fuerit luna,


RICHARD C. DALES

grossiciem suarum partium et viscositatem non patitur divisi- onem nec expirationem sed turgessit 30 se et eructat 31 propter 32 vapores inclusos. Aqua vero dulcis que subtilis est et pene- trabilis in suis partibus cum in ea adgenetur 33 aliquis vapor

150 expiratur34 statim nec proprie 35 patitur augmentationem. Item si corpus celeste non agit in 36 inferiora nisi 37 secundum suos radios luminares et ex hiis radiis 38 luminaribus cum incorporentur aliquomodo cum elementis et reflectendo intersecant se in puncto uno 38 sic distrahendo 39 partes materie 40 motibus diversis et in partes diversas aggenerant calorem, sicut [V 403B] patet in ultima propositione De Speculis.d 41 Unde quanto 42 fuerit materia subtilior tanto minus ex radio adgeneratur calor.e

semper linea exiens a centro terrae usque ad corpus lunae ostendit cacumen summum tu- moris praedicti. Sicut enim movetur luna ab oriente in occidentem, similiter movetur tumor ille. Et sicut luna totam terram circuit in die et nocte, similiter circuit tumor ille. Et cum movetur luna ad augen deferentis, crescit humor ille, et cum recedit ab auge, minuitur. Et sic, cum sit luna in auge, tunc est fluxus maris maximus, sicut in omni coniunctione eius cum sole et oppositione. Cum autem est in opposito augis, tunc est fluxus maris mini- mus, ut patet in septimo die lunae et 21ma, et apparet luna quasi semicirculus. Et sicut apparet de operibus solis et lunae in istis inferioribus, similiter de ceteris planetis con- siderabis. Unde manifestum est, quod omnes planetae, quanto a terra remotiores sunt, tanto fortiores, quanto propinquiores tanto debiliores in istis inferioribus habent operationes."

29 AP per. 30 FP transgessit; V transgredit. 31 F se et eructat deest; P se deest; et exsur-

git; V se deest; et erectat. 32 F super. 33 FP generatur; V generetur. 34 F expirat. 35 Coni. AF propria; P ut propter ea; V

propter hoc. 36 A in deest. 37 A Ut. 38FP radiis . . . uno deest. 39 p distruendo. 40 p in. dCf. Euclidis Catoptrica, Prop. 30 (Opera

omnia, ed. I. L. Heiberg [Leipzig, 1895], Vol. 7, pp. 341-343): "E speculis concavis adversus solem conversis ignis adcenditur .. ." Idem opus, videlicet Euclidis Catoptrica, citatum est a Roberto etiam apud De lineis, angulis et figuris: "Quid etiam possit reflexio. patet in corporibus politis et maxime in concavo, quoniam in libro De speculis probatur, quod speculo concavo ad solem posito ignis accenditur in eo, quod, ut praetactum est, omnes radii reflexi a superficie corporis concavi con- currunt ad punctum unum, et in illo puncto et circa est locus combustionis, sicut in libro

praedicto declaratur. Unde si stupa vel lana vel aliquid de facile combustibile apponatur loco, ibi comburetur" (Baur, op. cit., pp. 70- 71); De impressionibus elementorum: "Item radii reflexi a speculo concavo generant ignem ut stupa apposita inflammetur" (Baur, op. cit., p. 88); De colore: "Sed in puncto colligitur lux multa, cum speculum concavum opponitur soli et lux cadens super totam superficiem speculi in centrum sphaerae speculi reflectitur. Cuius etiam lucis virtute in ipso centro col- lecta combustibile citissime inflammatur" (Baur, op. cit., p. 78); De iride: "Hoc autem manifestum est per experimentum illud quod ponitur principium in libro De speculis: si in vas mittatur quid, sumatur distantia, ut iam non videatur et infundatur aqua vide- bitur, quod immissum est" (Baur, op. cit., p. 74); De calore solis: " Quod enim ex collec- tione radiorum aliquid calidum generetur secundum causam univocam caloris, patet per secundum De speculis quod hoc speculo concavo ad solem posito accenditur" (Baur, op. cit., p. 81). ". .. .sed radii solis cadentes deor- sum super planum terrae vel concavum, vel convexum reflectuntur secundum angulos aequales, ut patet ex ultimo principiorum doc- trinae De speculis" (Baur, op. cit., p. 83).

41V Explicit tractatus de fluxu maris seq. 42 p quamdiu. e Cf. Roberti Grosseteste De colore: " Color

est lux incorporata perspicuo" (Baur, op. cit., p. 78); De calore solis: " Radius enim in diaphano densiori habet maiorem incorpora- tionem, quam in subtiliori; . . . ex hac autem incorporatione secum distrahet partes aeris, scilicet cum colliguntur radii in punctum unum, in ipso puncto unusquisque secundum unam viam rectam, et propterea prope ipsum punctum erit maxima distractio aeris in partes diversas; et ita erit disgregatio et consequitur calor" (Baur, op. cit., p. 81); De iride: "Erunt igitur in universo quattuor diaphana, per quae penetrat radius solis. . . . Necesse est igitur . . . radios solares primo frangi in con- tiguitate aeris et nubis et deinde in contigui- tate nubis et rorationis, ut per has fracturas

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ROBERT GROSSETESTE'S QUESTIO DE FLUXU ET REFLUXU MARIS

Propterea 43 magis manent nives in summitatibus montium quam in vallibus eo quod est ibi aer subtilior.f Si ergo aqua dulcis

160 multo subtilior est 44 aqua marina 45 multo minus [F 19A] incorporabuntur radii lunares 46 in aqua dulci quam in aqua 47 marina et sic minor aggenerabunt calorem et minorem effectum. Tantum 48 sufficiat de prima parte huius questionis.

II

Ad secundam partem 1 accedamus in qua 2 inquirere 3 oportet causam 4 quare in quodam tempore augmentatur accessio et fit fortis, in alio tempore minuitur accessio et fit debilis. Et sunt huius 5 8 cause.

Prima est quod in coniunctione lune cum sole vigoratur virtus lune et fit accessio multa et fortis.6 In recessione autem lune a sole minuitur quousque distiterit 7 a sole secundum unam quartam circuli. Ab illo autem loco quousque veniat 9 ad semicirculum augmentatur eius 10 virtus non propter respec-

10 tum 11 ad solem sed propter 12 augmentationem luminis 13 in ea. Et iterum ab illo loco quousque distiterit 14 secundum 3 quartas minuitur accessio maris et iterum augetur quousque coniungitur soli; et sic proportionaliter secundum15 quattuor partes unius mensis respondentes IIII partibus unius diei.

Causa secunda est comparatio 16 diversa 17 diversi motus lune ad medium motum 18 lune. Si enim ex motu lune est motus maris ex 19 medio motu lune est medius motus maris 19 et ex

concurrant radii in densitate rorationis . . . Cum autem color sit lumen admixtum cum diaphano, diaphanum vero diversificetur secundum puritatem et impuritatem, lumen autem quadrifarie dividatur, . . . varietas coloris in diversis partibus unius et eiusdem iridis maxime accidit propter multitudinem et paucitatem radiorum solis" (Baur, op. cit., pp. 76-77); De cometis: ". . . non est radiositas reflexa visibiliter nisi cum radii reflexi ad- miscentur dyafono naturali terrestri, non ce- lesti" (S. H. Thomson, "The Text of Grosse- teste's De cometis," Isis, 1933, 19:19-25, on p. 19).

43 A Preterea; F Propria. f Cf. Roberti Grosseteste De impressionibus

elementorum: ". . . radii reflexi et condensati causa sunt caloris generati apud nos. Cuius signum est, quod in convallibus maior calor est quam in montibus; unde in montibus diutius manet nix quam in convallibus; unde etiam in quibusdam montibus altissimis manet nix perpetua" (Baur, op. cit., p. 87); De natura locorum: ". . loca montuosa magis calefiunt quam valles, quia radios et pyramides breviores recipiunt. Et hoc dico essentialiter, quia acci- dentaliter contingit in multis locis montuosis dominari frigiditatem . . ." (Baur, op. cit., p. 65); De calore solis: "Unde etiam in suprema tunica aeris, ubi est aer maxime

subtilis, minime generatur in eo calidum, quod patet experimento. In summitatibus enim montium abundant nives, ubi radii solares clariores sunt, quam in convallibus, et tamen est ibi reflexio radiorum sicut in valle; sed propter subtilitatem aeris ibi est densitas aeris parva . . ." (Baur, op. cit., p. 84).

44P est deest. 45 FP maris. 46 A luminares. 47 FP aqua deest. 48 FP Et hoc. 1AP partem deest. 2 A in qua deest. 3 F inquirere deest. 4F querere seq. 5 F hec; P VII cause vel seq. 6 p multo fortis. 7 FP distet. 8 AF unam deest. 9 FP venerit. 0 A eius deest.

11 FP lectio incerta. 12 A propter deest. 13 FP lune. 14 FP distet. 15 F super; P sunt. 16 A operatio. 17 A diversa deest. 18 F motus; P totus. 19 AP ex ... maris deest.

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RICHARD C. DALES

diverso 20 diversus. Unde cum diversus motus addit supra medium erit accessio differens 21 augens 22 super accessionem

20 mediocrem et cum 23 minuens minuens.24 Tertia causa est accessio lune ad augen sui circuli, id

est ad longitudinem 25 longiorem a terra. Tunc enim minoratur eius virtus in mari propter eius 26 elongationem a terra 27 et cum 28 accedit ad 29 oppositionem augis, id est ad longitudinem propinquiorem terre, augetur 29 sua virtus et est tunc fortis maris accessio.

Quarta causa est declinatio lune secundum latitudinem a circulo signorum versus austrum; tunc enim accedit ad medium occeani in quo est initium fortis accessionis. Cum autem

30 declinat secundum latitudinem a circulo signorum versus septentrionem propter recessum eius a medio occeani minoratur eius 30 accessio.

Quinta causa 31 est existentia lune in signis australibus vel 32 septentrionalibus et hec est 33 causa particularis 34 accessionis. Existens enim luna in signis australibus 32 auget accessionem ibidem. Existens vero 35 in signis septentrionalibus auget accessionem in mari septentrionali.

Sexta causa sunt dies qui ab antiquis 36 vocantur Egyptii g quia 37 ipsi primo invenerunt eos quam causam obmittamus ad

40 presens eo quod multum lateat effectus38 in eis. Septima causa est ex adiutorio solis et est sol ab equi-

noctio 39 vernali 40 usque ad solstitium estivale augens accessionem. Ab illo autem usque ad equinoctium autumpnale 41 minuens. Ab 42 illo autem usque ad solstitium yemali augens iterum; et ab illo usque ad equinoctium vernale minuens.42 Et [A 262B] erunt hee 4 quarte [F 19B] anni sicut et prius quattuor quarte mensis respondentes 4 quartis diei.

Octava causa est ventus. Cum fuerit ex parte unde est 43 accessio auget accessionem; cum autem44 in contrarium minuit.

50 Si ergo dividamus causas augmentationis 45 accessionis videbimus [P 42A] quod 45 aut erit causa accidentalis aut essentialis. Essentialis est 47 communis, et 48 propria accidentalis. Hec est octava 49 causa 50 communis, vero 51 septima 52 alie 53 autem proprie. Omnis enim stella habet operationem specialem ex natura speciali sua et communem in communicatione 54 cum stellis aliis. Et hec sufficiant de secunda parte.

20 A diversis. 21 P diminuens. 22 A augens deest. 23 F ear; P causa. 24 FP minuens deest. 25 P longitudinem deest. 26 FP eius deest. 27A a terra deest. 28 F tunc. 29 A ad . . . augetur deest. 30 A hec. 31 A causa deest. 32 p vel . . . australibus deest. 33A est deest. 34 A partibus. 35 FP autem. 36 A ad antiquos. g Cf. Lynn Thorndike, A History of Magic

and Experimental Science, Vol. 1 (New York:

Columbia Univ. Press, 1923), pp. 685-688. 37P qui. 38A affectus. 39 FP equinoctiali. 40 Coni. Codd. yemali. 41 FP septentrionale. 42 A Ab . .. minuens deest. 43 FP cum. 44 P e contrario seq. 45 P vel seq. 46 p que. 47 FP est deest. 48 P erit. 49A 4. 50 FP causa deest. 51 F aut. 52 F propria. 53 P alii. 54 FP connexam ex coniunctione.

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III Ad notitiam autem tertie partis 1 questionis,2 sciendum

est quod quedam flumina et quidam fontes patiuntur accessum et recessum non propter sui naturam sed quia continui sunt cum 3 aquis marinis; et non refert 4 utrum hec 5 continuacio sit in canalibus subterraneis vel in canalibus apparentibus in superficie terre.

Marium 6 siquidem tria sunt genera: Quedam enim sunt que non paciuntur accessum vel 7 recessum; quedam autem patiuntur sed non videntur; quedam autem 8 patiuntur et viden-

10 tur. Que 9 non patiuntur hoc erit per defectum cause materialis vel efficientis. Causa vero materialis duplex est. Una est quod oportet aquas congregari '0 in loco lato 1 et profundo. Et dico locum latum et profundum quoniam accessus aquarum in yeme ad eum non facit apparentem12 augmentationem nec recessus in estate per consumptionem caloris 13 solis 14 apparentem diminutionem. Propterea mare illud quod dicitur latum 15 in quo non 16 est sensibilis augmentatio et diminutio non patitur accessionem vel recessionem.17 Aliud genus maris est 18 in quo non vincit 19 duricies terre sed habet spongiosam, unde cum aqua ibi

20 subtiliatur per motum lune ingreditur 20 poros terre et non ascendit ad superficiem 21 terre. Tertia causa est distantia multa a motu lune sicut est in aliquo 22 mari septentrionali.23

Aliud genus maris est quod patitur accessum et recessum 24 et non videtur et tribus similiter generibus continetur. Unum est mare multam habens latitudinem ita quod unum litus eius 25 fuerit edirecto 26 lune et ibi fit accessio et recessio.27 Sed non videtur quia non sunt ibi habitatores cum litus eius'28 sit succedens 29 ad 30 partes terre inhabitabiles. In reliquo autem 31 litore, cum ibi sint habitatores, non apparet pro 32

30 magna sui distantia a motu lune. Aliud genus est cum apud utrumque litus fuerunt 33 habitatores sed pre 34 magna eius latitudine 35 aque que sunt prope pedes maris et multum dis- tantes a medio sunt aliquantulum subtiliate. Unde cum moventur a luna 36 exspirant sicut aque dulces neque 37 apparet in eis 38 accessio, etsi sit aliqua. Tertium genus est illud quod habet aliquantulum terram 39 cavernosam, in cuius poris et cavernis

1A partis deest. 2 FP questionis deest. 3 FP cum deest. 4 A refertur. 5 P hec deest. 6 P maria. 7FP et. 8 FP autem deest. 9 A quod. 10 A aggregari. 11 A lato deest. 12 P ad punctum. 13 P naturalis seq. 14P ad seq. 15 A latus. 16 A non deest. 17 A ad seq. 18 P est deest. 19 P manent. 20 F in seq.

21 A super faciem. 22 A super faciem. 23 A ad seq. 24 FP accessionem et recessionem. 25 F cum. 26 F e directe; P adirecto. 27 A et recessio deest. 28 FP illud. 29 FP accedens. 30A ad deest. 31P vero. 32F ita; P ibi. 33 F homines seq. 34 FP per. 35 F latitudinem; P sui altitudine. 36 F alia; P aliqua. 37 F nec; P et sic. 38 FP aliqua seq. 39 A cannosam vel seq.


RICHARD C. DALES

sunt vapores grossi quos 40 poros vel cavernas non ingreditur aqua 41 propter sui grossiciem et retentionem vaporum. Sed [F 19c] cum moventur 42 a43 luna subtiliatur aqua 44 et

40 expirantur 45 vapores illi 46 et ingrediuntur aque ad partes inferiores, et in parte superiori expirat eo quod est mare 47 subtilius ceteris maribus 48 et sic confluunt 49 aque motibus contrariis ad superius et 50 inferius; nec 51 apparet in eis accessio vel recessio,52 etsi sit aliqua.

Cetera 53 autem in quibus est et apparet paciuntur similiter secundum magis et minus.

Translation of An Inquiry into the Causes of the Tides *

I In our investigation of the tides, let us first determine the material cause,

which is twofold, namely general and specific. The general cause is this: The spheres of the four elements are so

arranged that earth is in the center and fire on the periphery, while water and air occupy places between these two. These elements are of such a nature that they can be moved by rarefaction and condensation. But water and air share this capacity to a greater extent than fire and earth; therefore they are better suited to be moved. The minor premise is proved thus: Condensation is the motion of the parts of matter toward the center of the universe, and rarefaction is the motion of the parts of matter toward its periphery. Therefore, that which is in the very center, such as earth, is not further condensable; and that which is at the periphery, such as fire, cannot be further rarefied. However, those things which are between the center and the periphery, such as water and air, can be rarefied and condensed.

Now for the specific material cause: Every motion of a generable or corruptible thing takes place in water and air. Let us omit the motions of the air and speak about the motions of water.

This investigation has three parts. The first part concerns the material and efficient cause of such motions. The second part concerns the reasons for the increase and decrease of the tides. The third part concerns the three kinds of seas: those which have tides, those which do not have tides, and those which have very small tides but do not seem to have any.

40 F vapores vel seq. 41 FP aqua deest. 50 A in. 42 A movetur; P aliqua subtiliatur seq. 5 P ut. 43 P a deest. 52 P eas accessus vel recessus. 44 F aqua deest. 53A Ceca. 45 FP expirant. * I wish to thank my colleague, Professor 46A illi deest. Thomas W. Africa, and Professor Ven Bul- 47P mare deest. lough of San Fernando Valley State College 48 F maribus deest. for checking my translation and making help- 49 FP effluunt. ful suggestions.

468



Turning our attention to the first part, let us first determine the efficient cause. This efficient cause must necessarily be a power of the sky or the power of a star in the sky. For an element is not moved by itself or by another element, but we ought to reduce every motion of the elements to an efficient cause which is an immaterial species.

In this connection, Alpetragius says that all the lower spheres, as far as the sphere of water, are moved from east to west by the power of the outermost sky. But the lower any particular sphere is, the less power it will receive from the outermost sky, because this power is the power of a body and diminishes with distance. The earth, however, both because it is farthest away from the outermost sphere and because of its heaviness, remains completely immobile. Therefore, the water of the sea is moved by the power of the outermost sphere from east to west, and from this, Alpetragius says, a crashing together of the waters occurs and consequently a high tide. But the water returns to its original place because of its heaviness, and when it has all returned it begins to be moved again and to rise as far as its heaviness will permit, and then again it returns. And these two high and low tides take place in a time greater than one day and night.

That this is false is clear thus: In the outermost sky, the parts which are moved most rapidly are the parts existing on the equinoctial circle, directly under which, on the surface of the earth, is the great sea called Ocean, surrounding the land; and this is the source of all seas. Therefore, if in one part of the sky there were a motive force and in another part there were not, when this part of the sky rose one part of the sea would be moved by it and another would not. If, therefore, one part of the sea should be moved and another not, the one part would resist the other, and one part would have to be elevated above the other and occupy a greater place. But since the sea is circular, and the motive power operates equally in every part of the equinoctial circle, therefore all the parts of the sea under each single part of the equinoctial circle will be moved equally in the same direction. Therefore, one part of the sea will not resist the motion of the other part, and there will be no reason why the water should occupy a greater place. Likewise, if the sea were moved in this manner, only local motion would result from such a cause. But we perceive by experience that the rise and fall of the sea results from its condensation and rarefaction. For ships in the sea draw less water at high tide than at low tide, and this is because the low tide is caused by rarefaction and the high tide by condensation. Also, the water is found to be hotter at high tide than at low, and this can only be because of the greater subtlety of its parts. These arguments and experiments are sufficient to prove Alpetragius' explanation false.

That the moon alone, and not some planet or image of the fixed stars, is the cause of this motion is clear for this reason, that the motion of the sea follows the motion of the moon more closely than that of any other planet; and there is a definite proportion between these two motions, as will


RICHARD C. DALES

be made clear below. The arguments of the astronomers lead us to a similar conclusion. They point out that there are two great luminous bodies, the sun and the moon. Of these two, the sun is primarily responsible for motions which take place in the air, and the moon for those which take place in water, since in these two spheres [i.e., air and water] the generation and corruption of all living things takes place, and these two luminous bodies are the principal causes of every generation and corruption. Also we know by experience that, of all the heavenly substances, the moon exercises the greatest control over moist and cold bodies. Thus certain people are called lunatics because, when the moon wanes, they suffer a diminution of the cerebrum, since the cerebrum is a cold and moist substance. These arguments are enough to show that the moon is the sufficient and efficient cause of the tides.

But how it causes them, we must still discover. When the moon rises on the horizon of any sea, it first casts its luminous rays on the center of that sea and, strongly impressing its power, it moves this sea, and this motion increases until the moon arrives at the meridian. But when it passes over the meridian its effective power is diminished, and the sea recedes toward its original place until the moon has set. When the moon again passes over from the west to the middle of the sky under the earth, the sea is increased; and when the moon passes from the middle of the sky under the earth, the sea is decreased until the moon again begins to rise. And thus in one revolution of the moon from rise to rise, two high tides occur in that place over whose horizon the moon has risen.

However, the explanation of why the high and low tides correspond to these four quarters of the sky is very difficult. It is clear enough from what has been said why the high tide occurs between the moon's rise and its arrival at the meridian and why the low tide occurs when the moon is passing from the meridian to the western horizon. For while it is rising it impresses its power more strongly than when it is setting. But the other high and low tide take place when the moon is in the two quarters below the horizon, and its light cannot act on the sea. Since heavenly bodies can only act on lower bodies by their light, it is doubtful how the moon can be the cause of the motion of the sea. The astronomers answer this by saying that opposite quarters of the sky have similar effects, but whether this is true remains to be proved and is in need of further investigation.

Therefore the time taken by two complete high and low tides exceeds the time of one day and night by the same amount as does one revolution of the moon from rise to rise. You must find out, therefore, by how many hours the rise of the moon follows or precedes the rise of the sun. We know by how many hours the beginning of the rise of the sea follows or precedes the beginning of the day and that one lunation contains twenty-nine days and a few minutes. Therefore, in seven and a quarter days and a few minutes the moon will be one-quarter of a circle east of the sun; whence in one-third of this time, when the sun is beginning to rise, the moon will be in the middle of the sky under the earth, and then the tide will begin to

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recede, since at the beginning of this time the tide began to rise. In twice this time, however, when the sun is in the east and the moon is in the west, the tide will begin to rise. But if the moon should be more than three- quarters away from the sun, when the sun begins to rise, the moon will be in the middle of the sky above the earth, and the tide will begin to recede. However, when the moon is again in conjunction with the sun, the beginning of the day and the beginning of the rise will occur at the same time. And this is what sailors say, that if the beginning of the rise coincides with the beginning of the day, seven days later the beginning of the recession will coincide with the beginning of the day. But this rise and fall in the same times does not appear on the shores of seas which are far away from the middle of that sea where the rise and fall of the tides originate. And you should know that on the shores nearer to the south and east, the rise takes place more quickly. Let this suffice concerning the efficient cause.

Now it remains to discuss the specific material cause, and it is this: Waters tend to come together in a deep and broad place, and in these waters is much matter of vapors and winds. Whence the moon, rising and impressing its power, generates many vapors in these waters and stirs up the winds. But this water, because of the heaviness and viscosity of its parts, will not let them escape, but rumbles and becomes swollen because of the trapped vapors. But since fresh water is subtle and its parts are penetrable, when any vapor is generated in it, it is expelled at once; hence it does not, strictly speaking, have tides.

Also, if a heavenly body acts on lower bodies only by its light rays, since these light rays are in some manner incorporated with the elements, they intersect themselves at one point when they are reflected, and thus they generate heat by scattering the parts of matter in various directions, as is clear from the last proposition of Euclid's Catoptrica. Therefore the subtler the matter, the less heat will be generated by the ray. For this reason, snow remains longer on the tops of mountains than in valleys because the air is subtler there. Therefore if fresh water is much more subtle than sea water, the lunar rays will be much less incorporated in it than in sea water, and thus they will generate less heat and a smaller effect. Let these remarks suffice concerning the first part of our investigation.

II Let us go on to the second part, in which we are to seek the reason why

sometimes the tide increases and becomes strong and at other times it decreases and becomes weak. There are eight reasons for this.

The first is that when the sun and moon are in conjunction, the power of the moon becomes stronger, and the tide increases and becomes strong. But as the moon recedes from the sun, the tide decreases until the moon is one quarter of a circle away from the sun. From this point until the moon is a half-circle away from the sun, its power increases, not because of the moon's nearness to the sun but because of the increase of light in it. And again, from this point until the moon is three quarters away from the sun, the tide decreases; and then it increases again until the sun and


RICHARD C. DALES

moon are in conjunction. And this occurs proportionately according to the four parts of one month corresponding to the four parts of one day.

The second reason is the comparison of the diverse motion of the moon with the mean motion of the moon. For if the motion of the sea is caused by the motion of the moon, then the mean motion of the sea should correspond to the mean motion of the moon, and the diverse motion of the sea to the diverse motion of the moon. And so, when the moon's true motion varies from the mean motion in one direction, the tide is increased; and when it varies in the other direction, the tide is lessened.

The third reason is the approach of the moon to the aux of its circle, that is to its longitude farthest from earth, for then its power on the sea is diminished because of its greater distance from earth. And when it approaches the point opposite the aux, that is its longitude nearest the earth, its power increases, and then the rise of the sea is strong.

The fourth reason is the southward declination of the moon in latitude from the zodiacal circle, for then it approaches the middle of the Ocean in which the strong rise begins. However, when the moon declines north of the zodiac, the high tide is lower because of the moon's greatest distance from the middle of the Ocean.

The fifth reason is the existence of the moon in the southern or northern signs of the zodiac, and this is a particular cause of the high tide. For when the moon is in the southern signs, it increases the high tide in the corresponding place on earth. But when it is in the northern signs, it increases the tide in the northern sea.

The sixth reason is the days which are called " Egyptian days " by the ancients, because the Egyptians first discovered them. But let us omit this reason for the present because many effects lie hidden in these days.

The seventh reason is the help the sun gives the moon. From the spring equinox to the summer solstice, the sun increases the tide. But from that point to the autumnal equinox, it diminishes it. From the autumnal equinox, however, until the winter solstice, it increases it again. And from there to the spring equinox, it diminishes it. And there are these four quarters of the year, just as earlier we noted the four quarters of the month corresponding to the four quarters of the day.

The eighth reason is the wind. When it blows in the direction of the tide, it increases it; but when it blows in the opposite direction, it decreases it.

If, therefore, we make a classification of the reasons for the increase of the tide, we shall see that each cause will be either accidental or essential. The essential cause is general, and the accidental cause is specific. This eighth cause is general, but the seven others are specific. For every star has a special operation as a result of its special nature and a general operation in common with other stars. And let these remarks suffice concerning the second part.

llI For a knowledge of the third part of our investigation, we must be aware

that certain rivers and springs have tides not because of their own natures but because they are continuous with the waters of the sea; and it does not

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matter whether this continuity is in underground channels or in channels appearing on the surface of the earth.

There are three kinds of seas. There are some that do not have tides, some that have tides but do not seem to, and some which have tides and seem to. If a sea does not have tides, this will be because of the absence of a material or efficient cause (and remember that the material cause is twofold). One instance of this is that waters tend to come together in a deep and broad place. I say a deep and broad place since, when the waters come together there in the winter, they cause no apparent increase; nor, when they leave it in a summer because of their consumption of the sun's heat, is there an apparent diminution. For this reason, that sea which is called broad, in which there is no sensible increase or decrease, does not have tides. Another example of this kind of sea is that in which the hardness of the earth is not sufficient, and the earth is spongy. So when the moon makes the waters more subtle there, the water enters the pores of the earth and does not rise to the earth's surface. A third reason is the great distance from the motion of the moon of a certain northern sea.

Another kind of sea is that which has tides and does not seem to; and there are similarly three kinds of these. One is a sea which is very wide so that one of its shores is near the moon's motion, and on this shore there are tides. But they are not seen because no one lives on that shore. On the other shore, however, where there are inhabitants, no tide will appear because it is too far away from the motion of the moon. Another kind is when there are inhabitants on both shores, but because of its great width, the waters which are near the bottom of the sea and far distant from its center are somewhat rarefied. So when they are moved by the moon, they let the vapors escape, just as fresh water does, and no tide is apparent in them although there is a very slight one. The third kind is that which has somewhat cavernous earth, in whose pores and caverns are heavy vapors. The water does not enter these pores and caverns because of its heaviness and its retention of vapors. But when the vapors are moved by the moon, the water becomes more subtle; these vapors are expelled and the waters enter the lower parts. And in the upper part it expels them so that the sea is more subtle than other seas, and thus the waters flow together by contrary motions both upwards and downwards. No tide is apparent in seas of this kind, although there is a slight one.

Other seas which have tides, and seem to, behave similarly to a greater or lesser degree.

APPENDIX

Many of the differences between my text and that of Professor Frances- chini are minor and make little or no difference in the meaning. Several, however, are of considerable importance. Among the latter, I call attention to the following:

I, 127. Here manuscripts P and V supply the perfectly acceptable reading: "Hoc autem tempore duplicatio erit . . . ," in place of the "duplato" of AF, accepted by Franceschini.


RICHARD C. DALES

II, 41-42. The manuscripts and Franceschini's text all contain the obvi- ously incorrect "yemali " in place of " vernali." Any doubt as to the correct reading is dispelled by the fact that the sun moves from this point to the summer solstice, the autumnal equinox, and the winter solstice, and back to the vernal equinox.

II, 51-54. All the manuscripts are bad here, and Franceschini added to the difficulty by misreading " 7a" in A as "alia." He reads the whole passage: ". . videbimus quod aut erit causa accidentales, aut essentialis. Essentiales, communis et propria. Accidentalis hec est octava, communis vero alia, alie autem proprie." But this does not mean anything. I read it as: ". . . videbimus quod aut erit causa accidentalis aut essentialis. Essen- tialis est communis, et propria [est] accidentalis. Hec est octava causa communis, vero septima alie autem proprie." Admittedly, we still seem to have an extra "vero" or "autem," but the meaning is clear, and it corresponds accurately to the preceding discussion of the eight causes.

III, 7-10. Syntactical probabilities alone would favor Franceschini's reading here, but then the passage would not mean what it must mean in the light of what follows. Therefore we must change the punctuation (with P) and read " que " with FP in place of " quod." This gives the reading " quedam autem patiuntur et videntur. Que non patiuntur, hoc erit per defectum cause materiali vel efficientis " in place of Franceschini's "quedam autem patiuntur et videntur quod non patiuntur. Hoc erit. . .." Franceschini's reading makes a better sentence, but it also makes the second and third kinds of seas difficult or impossible to distinguish. The last line of the treatise makes clear beyond any doubt the characteristics of this third kind of sea and justifies our reading: " Cetera autem in quibus est et apparet patiuntur similiter secundum magis et minus."

III, 39. In accordance with the author's scheme, the subject must be " vapores " rather than "aqua," so we must read "moventur" with FP in place of " movetur."

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Issue Table of ContentsIsis, Vol. 57, No. 4 (Winter, 1966), pp. 409-654Volume Information [pp.645-650]Front Matter [pp.409-515]Maxwell and the Direct Experimental Test of His Electromagnetic Theory [pp.411-432]Hooke's Vibration Theory and the Isochrony of Springs [pp.433-441]Characteristics of Chinese Astrology [pp.442-454]Documents and TranslationsThe Text of Robert Grosseteste's Questio de fluxu et refluxu maris with an English Translation [pp.455-474]The Earliest Extant Arabic Arithmetic: Kitab al-Fusul fi al Hisab al-Hindi of Abu al-Hasan, Ahmad ibn Ibrahim al-Uqlidisi [pp.475-490]

News [pp.491-493]Correction: News [p.493]ReviewsHistory of Science on the Silver Screen [pp.494-497]

History of Scienceuntitled [pp.497-498]

Philosophy of Scienceuntitled [pp.498-499]

Sciences of Manuntitled [pp.499-500]

Classical Antiquityuntitled [pp.500-501]

Renaissanceuntitled [pp.501-504]untitled [pp.504-505]

Seventeenth & Eighteenth Centuriesuntitled [pp.505-506]untitled [pp.506-507]untitled [pp.507-508]untitled [pp.508-509]

Nineteenth & Twentieth Centuriesuntitled [pp.510-511]

Contemporary Sciencesuntitled [pp.511-513]

Ninety-First Critical Bibliography of the History of Science and Its Cultural Influences (To 1 January 1966) [pp.516-644]Back Matter [pp.651-654]

isis volume 57 issue 4 1966 [doi 10.2307%2f228517] richard c. dales and robert grosseteste -- the...

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