1857.] of Gold (and other Metals) to Light. 4*33 



here ; which would seem to imply that the particles are so 

 small and so near, that two or more can act at once upon the 

 individual atoms of the vibrating ether. Their association is 

 such as to present as it were an optical continuity. 



The gold films by phosphorus were then submitted to ex- 

 periment, and gave exactly the same result. All of them de- 

 polarized, and required direct rotation of the analyser to ar- 

 rive at a minimum, or to pass from the red to the blue tints. 

 Graduated films, of which I should judge from the depth of 

 tint that one place was at least twenty times as thick as an- 

 other, gave the effect as well in the thinnest as the thicker or 

 any intermediate part ; indicating that thickness of the plate, 

 and therefore any quality equivalent to crystalline force of the 

 particles, had nothing to do with the matter. A glass beaker, 

 which had been employed to contain ruby fluid, had a film of 

 gold deposited on its inner surface so thin, as to be scarcely 

 perceptible either by reflexion or otherwise, except by a ruby 

 tint which appeared upon it in certain positions ; but being ex- 

 amined by a polarized ray, it gave an effect as strong and as 

 perfect as gold-leaf, showing how thin a film of gold was suffi- 

 cient for the purpose. This thin film appeared to be almost 

 perfect in its continuity, for when the red image was brought 

 in, direct rotation of the analyser reduced it to a minimum 

 which was quite dark ; after which, further rotation brought 

 in a good blue image. The least touch of the finger removed 

 the film of gold and all these effects with it. These films, 

 though they are certainly porous to gas, and to water in some 

 form, for it can evaporate from beneath them through its body, 

 have evidently optical continuity. 



In order to submit the gold fluids to experiments, cells were 

 made of two glass plates, separated by the thickness of a card, 

 and fastened at the edges by varnish internally and gum ex- 

 ternally. These being filled with dense ruby or blue fluid, 

 gave no indication of action on the ray, showing that the 

 diffused particles were inoperative. The same fluids, dried 

 on plates of glass so as to leave films, did act just as the gold 

 deflagrations had done ; for though the particles were very 

 irregularly spread, parts of the general deposit, and these not 

 the thickest, could be selected, which produced the effect 

 excellently well. 



