588 EASTMAN KODAK COMPANY NOTES. [J. F. I.

enhancement of brightness contrast, elimination of haze, obtain- ing moonlight effects, etc., is given. The last section of the paper deals with the handling of panchromatic fihn in the dark room. The questions of satisfactory safelights, dark room illumination levels, etc., are discussed.

IMPREGNATING W O O D W I T H PARAFFIN?

By L. W. Eberlin and A. M. Burgess.

SPRUCE impregnated with paraffin was found to withstand the action of acid and alkaline solutions with a minimum absorp- tion of moisture and consequent swelling. The experimental work conducted to determine the most suitable kind of wood, impregnant, and method of impregnation is described. A.prac- tical method for the large-scale impregnation of spruce with paraffin is given. It was found that for the impregnation of wood with paraffin and similar substances the degree of impregnation was enhanced by the presence of 15 to 2o per cent. or more of moisture in the wood.

ON THE RELATION BETWEEN TIME AND INTENSITY IN PHOTOGRAPHIC EXPOSURE, V?

By L. A. Jones, V. C. Hall, and R. M. Briggs.

THE effect of different developers and development times has been studied in detail. There is practically no difference in the curves of constant density for developers of widely different characteristics when development is carried out to the same point with each developer. A change in development time has no effect on the shape of the curves of constant density, but usually changes the position of optimal intensity. The results support the con- clusions that the variation in sensitivity of individual silver halide grains with intensity follows a law similar to that of the whole emulsion, that all silver halide grains follow the same function, differing chiefly in the intensity for which the sensitivity is a maximum, and that at all intensities a grain is either entirely unaffected by the light falling on it or made completely developable.

Communication No. 283 from the Laboratories of the Eastman Kodak Company and published in the Ind. and Eng. Chem., 19, January, I927, p. 87.

3 Communication No. 292 from the Research Laboratories of the Eastman Kodak Company and published in J. Opt. Soc. Miner., I4:223 (I927).