144 ANNUAL OF SCIENTIFIC DISCOVERY. 



rough on the surface with strong nitric acid, then washed with alcohol 

 and dried. This plate was exposed to the sun's rays for three hours, 

 and then one half of the polished part of it, and one half of the rough 

 part, were placed under an opaque screen, with the other portions 

 under a piece of transparent glass. The plate was then laid upon 

 albumenized paper prepared with chloride of silver. After twenty-four 

 hours' contact the same time as with the porcelain an impression of 

 the unpolished portion of the steel plate, acted upon by the light, was 

 obtained ; but none from the polished part, nor from the unpolished 

 portion which had been placed under the opaque screen. 



A strip of glass ground or roughened on the surface, and cleaned 

 with distilled water, gave the same results as the steel plate ; but under 

 a violet-colored glass, the light had less action than under a white 

 glass. 



In a paper upon this subject, M. Niepce de Saint Victor says : 



It has frequently been announced that light magnetizes a bar of 

 steel ; but after removing every source of error, I have found it impos- 

 sible to make a needle, solarized for a very long time under the rays 

 of light concentrated by a strong lens, attract another sewing needle 

 suspended by a hair, whether the light was white, or colored by being 

 made to pass through a violet-colored glass. 



I have also enveloped a needle in paper impregnated with nitrate 

 of uranium, or with tartaric acid, and solarized ; I have also suspended 

 a needle horizontally in tubes containing solarized cardboard, and the 

 results were invariably of a negative character ; which proves that the 

 activity of which I have spoken above is not due to electricity, as 

 some experimentalists have pretended. 



I afterward repeated the first experiments upon needles very feebly 

 magnetized, to see if I could de-magnetize them; but the results were 

 always negative. 



From which I conclude that this persistent activity given by light 

 to all porous bodies, even the most inert, in all my experiments, can- 

 not even be phosphorescence. It is, therefore, most probably a radia- 

 tion invisible to our eyes, which acts like a gas, since it does not pass 

 through glass. 



NEW APPLICATIONS OF PHOTOGEAPHT. 



Important Discovery in Photographic Science. Signer Balsamo 

 Prof, of Physics, University of Lucca, Italy, has found a substitute for 

 nitrate of silver, in the positive printing of photographs, viz., hydro- 

 chloric acid saturated with phosphorus, and diluted with acetate of cop- 

 per. Paper imbued with this compound is exposed to the action of 

 light under a negative, and when it has acquired a gray color, it is 

 removed from the pressure-frame and exposed for five minutes to the 

 vapors of sulphuretted hydrogen, which acts upon those parts of the 

 paper which have become altered by the action of light. The picture 

 is afterward toned and fixed in a solution of nitrate of bismuth. _ A 

 decomposition of the salt of copper takes place, and the image, which 

 is permanent, is formed of oxide of bismuth. 



Photographic Printing. Mr. Sutton, an English photographist, 

 proposes the following method of transferring a photograph upon wood 



