166 ANNUAL OF SCIENTIFIC DISCOVERY. 



he was able to exhibit the results of his experiments. He referred to 

 the relation of all substances to light and to their different refractive 

 and dispersive powers, as manifested in mixtures, pointing out how 

 exceedingly available color is in determining the chemical character 

 of a body. He first exhibited, by way of contrast, an impure spec- 

 trum produced by the introduction of a piece of silver in the light, 

 and then the pure, continuous spectrum of the lamp itself. He then 

 showed the varied action of the different rays of the pure spectrum, 

 caused by putting in the flame a peculiar salt of copper, some rays 

 being cut off and others rendered opaque. He next took two bodies 

 much alike in color, diluted port wine and diluted blood, and exhib- 

 ited their totally different spectra. In the spectrum of blood certain 

 rays were cut off or obscured, while two distinct red bands were man- 

 ifest, these last appeared in the spectra of several mixtures which 

 contained blood, and even in hsematine, an extract of that fluid. By 

 examining the spectrum of salts of iron it wus shown that the color of 

 the blood is not due to the presence of that mineral ; it was suggested 

 that it is probably derived from the. complex nature of its crystals. 

 Prof. S. stated that he had selected blood as a striking example of the 

 way in which the chemical character of bodies may be tested by their 

 relation to light. 



OPTICAL PROPERTIES OF THE METALS. 



M. Quincke's paper on this subject, published in the Philosophical 

 Magazine is devoted to the transmission of light through thin films of 

 metal, with especial relation to the researches of Faraday, who remarked 

 the irregularity of the intensity and color of the light in the same 

 metal. This, M. Quincke says, would have been attributed to the 

 presence of holes in the plate, if Faraday had not demonstrated the 

 property of a thin metallic film, viz : that, when placed obliquely 

 between two crossed XicoPs prisms, it illuminates the plate and acts 

 "just like a glass plate." This property, Al. Quincke thinks, was 

 first observed by Mr. Warren De La Rue, with regard to gold leaf, 

 and afterwards by Faraday in thin transparent plates of platinum, 

 palladium, rhodium, silver, copper, tin, lead, iron, zinc, and aluminum. 

 Faraday al. o found that by employing rhodium, polarized light, and 

 an arrangement of sulphate of lime plates, other colors than green 

 could be transmitted by the gold leaf. The details given by M. 

 Quincke in regard to his own experiments on this subject are too pro- 

 found for our pages and we only give a part of his results. " Light,' 1 

 he says, " penetrates to an appreciable depth into the metal, and 

 must also be reflected back from the interior ; for the great difference 

 of phase of the components of reflected light seems to "be only ex- 

 plicable on 1 he supposition that the reflected ray has to pass through 

 the boundary between the metal and the medium laying adjacent to 

 it." M. Quincke endeavored to determine directly the velocity of 

 light through metals, and obtained the remarkable result that light 

 travels fasti r through gold and silver than through a vacuum. He 

 says, finally, that he was unable to detect any difference of phase in 

 the compoi.eiits of the light which had previously passed through 

 transparent substances such as plates oi' glass. "Therefore the an.r 

 ology between metals and transparent bodi . which Jamin has proved 

 for refracted light, is not maintained tor reflected light. 11 



