AXERICAN MECHANICS'MAGAZJNE, 187 are two feet. ‘IIe running wheelsbeing four feet diameter, \vi,vith flanges on their edges.

'h wkt- 1s supphl to the boiler, by pipes leading from a cistern carried in a cart, and attached behind the en ine ; the same cmt,ajsO carries the coals for feeding the furnace, mhrc 1 3 consumes about tkipe;ee qual,ters of 2% ton, in going a distance of fifty miles. _ji .

Certain parts Of thC hue of road, rise half an inch in a yfi;lr(i ; t1ri.s the power.of the engine overcomes readily, with twenty c&-iaweq,at_ tached to It, each containing about two tons weight, and pro&& as above sa& upon an average, at the rate of six miles per hour, on the first day of opening the rail-say, a train of thirty loaded ~va~ons, and a carrmge with passengers, was drawn alon some part C;i’ the line, at the rate of fifteen miles per hour ; bnt t us was doubtless a f;. mere experiment; the ordinary speed, is not likely to esceed six miles, as above stated : but this speed, and the employment of a plain rail, is certain1 tive carriages, near l!I

a considerable improvement upon the loconm- eeds, winch travel upon a rack or cogged rail,

and not faster than two and a half, or three milts, per hour,

sel, containing cold water, some gum adragant, havinp been well worked wit11 a wooden spatula, to free it from lunq~s. : ‘I’ rere must be a sufficient quantity of water, tence of a jelly.

to give to this diluted gum, the consis- Paper, and some sorts of stuffs, upon which, if this

con~posltion be smoothly applied, with a pencil, or a brush, and dried before a gentle fire, will receive either water or oii colours ; in using water colours, they must be mixed with a solution of the above gum. This cloth or paper, so prepared, will take any colour except ink. When it is intended to retouch any particular part of the drawing, it should be lvashed with a sponge, or clean linen, or a pencil, (contain- jnw some of the above-mentioned liquid;) if the part is only SWII, it Iv$ then rise quickly, and appear as if repainted.

fl Conzposition to render 1Vootl JiWproOf. By Dn, Fucns. Dr. Fuchs, member of the Academ 1 of’ Science, at Munich, is said.

to have discovered a composition, by,w i. nch he renders wood, incombus- tible; the composition is made of granulated earth, and an alkali. ‘1’0 obtain this composition, the inventor says, you must dissolve some moist, gravelly earth, which has beer: previously well cached, and cleared from any heterogeneous matter:, in a solution of caustic al- kali. This mixture has the property ot not becoming d~~on~posed by fire or water. When spread upon wood, it forms a vrtnous coat, aIn1 is proof against the two elements. The building committee of the royal theatre, havg twice publicly tried the efficacy of the colnpwition

165 'IIHE FBANKLLN JOURNAL AND

on two srlla11 buildings, of six or eight feet in length, an+d*of a propor- tionate heig-llt ; the one was covered with the composltro?, and the ot}ler built in the usual manner. The fire was put equally m the two l,uil~lin$r~ ; the GIW which was not covered with the coyposition, was consumed, whilst the other remained perfect, and entlre. The cost of this process, is very insignificant, compared to its Cgreat utili$,being about limo francs three ccntimcs per 100 square feet.

Tile ro>-$ tlleatre at, Munich has undergone this process, having &out 40&0c)0 srp-c Let; the expense of which was about 4 or 5OOU L’rnncs.

The lath Earl Stanho]~e made some veS,y successful experiments upon this subject, . he coated a building with sand and glue, which proved perfectly fire-proof.

_.__~ --- _-_.^_ .-- I__-,

ON ClfRoNOME’rERS.

To the IJnitcd States Gazette of the 8th inst. is a st%tement taken fioir) S?lc,n~dcn’s New York Advocate, of what is denominated ct a Cul.;ouf~i CIiScoi~ery” upon Lhe varialion of chronometers. It appears .th:+t or. Ilarvex, of li,ondon, by repeated experiments, has ascertain- cd that tile tlens+y of the medium m which a chronometer is placed, has a sci~s~blc in%ience upon its rate ; in other words, that a chrono- meter c~~:uuetcd in London, which is nearly on a level with the sea, wouitl u~c!ergn au n!tr:ration of rate from a difference of atmospheric l~es.:~re alone, if tlai:s lorted to Madrid, Mexico, or any other place, ~nuc:l above the level o 1, the place where it was constructed.

‘I’hc cause v, ill be Li)und in the balance. All chronometers that are :~:IJG yick11 by screws, will vary in their time, according to thaexperi- Mali o! $1~. l-lar\-ep. These screws having large heads, one on each side 0:‘ ihc balaiice, their line crossing the centre, and the loadings, the line of which crosses that of the screws at right angles, make

J80. ~~:~~~~iEClioizs, from the rim j these, in consequence of its velocity, strike the atiil~~~pliC?W with great relative force. The effect produced is, that in a mr~rr elevated situation, or less dense medium, than that in which the clironomr%1 was ad,justed, its motion will be faster, and so the contrary, in a lower or heavier atmosphere.

A chronomcler drops from 125 to 150 times in one minufe,accord_ ing to the calculution of the train; and a free, accurately made scapen~nt, with a force of main-spring in proper accordance with the weightof the balance, will always give that balance. an entire rcrolv,t~on, at least, to every dro

R The subscriber, at this time, has

one made by Uissctt, R0ya1 Exe ange, that throws its balance a re- volution arid a third, which gives it an action equal to two hundred complete circles, in one minute. When it is considered that the loadings of this balance, present a flat, and the screws, for adjust- ment, a round projecting surface to the atmosphere, and that all are upon its periphery, thrown back and forth, at the above rate, it will bo readily perceived, that different densities will, jn some degree, aGct the action, and consequently the time of the chronometer. 1~