NATURAL PHILOSOPHY. 199 



I considered this experiment as very encouraging, but having only 

 lately tried it, have not repeated it by itself without the agency 

 of electricity. 



As electricity is a powerful agent in decomposing chemical com- 

 pounds, it might be naturally inferred that it would aid in this process. 

 I have often tried it, but without, until lately, any very important re- 

 sults. Dry chloride of silver is not decomposed by electricity, yet its 

 decomposition by light and other agents may, by it, be much accele- 

 rated, and I did not at first use a sufficiently powerful current. I now ren- 

 der the plate a part of the conducting medium which terminates at the 

 positive pole, and terminate the poles in water, to which some saline 

 constituent has been added, and by the decomposition of the water 

 I am enabled to judge of the power of the current. By using the 

 gases at the same time that the plate is thus excited, I have been en- 

 abled to take pictures in from four to five minutes, which would other- 

 wise require from three to five hours for their production. These 

 pictures are developed under a hard, tough enamel of chloride of sil- 

 ver, cannot be rubbed out by the fingers, and will even bear consider- 

 able buffing, and, if the enamel is thick, are improved by the 

 operation. I have not been able to permanently fix the picture, 

 but it will keep a long time, if not exposed too often and too 

 long to the light. From the above experiments it seems that a 

 protonged exposure is not necessary to produce coloration, hence 

 agents of great energy may be employed in reducing the chloride. 



That coloration may be produced, it is important, I think, that 

 the picture by whatever process it is taken, be positive, and com- 

 plete on its removal from the camera. For fixing, it is important 

 that all the organic matter be destroyed, and then, I believe it will 

 be fixed. I am at present engaged in experimenting with iodine, 

 bromine, fluorine, sulphur, chrome, and copper, and their compounds, 

 deposited on the silver plate by electric action, or otherwise, but have 

 not, as yet, any results sufficiently matured to publish, though I have 

 produced coloration. Great care is requisite in preparing the en- 

 ameled plate of chloride, and some experience is required to judge at 

 what state of its preparation it is most sensitive to light, yet any artist 

 can, after a few experiments, prepare it. 



NEW METHOD OF ILLUMINATION. 



The following new method of illumination has recently been ex- 

 hibited in Paris, by M. Godillot. The principle is, that of the multi- 

 plication of light by means of innumerable small mirrors arranged in 

 a particular manner in a multitude of frames bound together ; and 

 which may take different forms, as that of a star, that of a cross of 

 the legion of honor, &c. This framing in li^ht wood-work, with its 



^5 ' ^j o ' 



mirrors, is placed perpendicularly, and made to rotate. In front of 

 its central point is placed a bright burner, the reflexion of which illu- 

 minates every mirror and multiplies the light infinitely. If between 

 the burner and this system of mirrors a colored glass is interposed, 

 18* 



