on the Absorption-Spectra of Metals. 237 



apart to render them very conspicuous in the field of view ; at 

 the same time there was continuous absorption in the blue. It 

 was specially observed that there was no absorption in the red. 



It may be interesting to note that the vapour of silver when con- 

 densed into fine particles, escaping into an atmosphere of hydrogen, 

 is blue by reflected light. 



Copper. — "With the greatest thickness only a continuous ab- 

 sorption in the blue could be obtained. 



Sodium. — Only the dark D line was observed, no traces of 

 channelled-space absorption being visible. 



Calcium. — We operated upon a small piece of metal prepared 

 by the late Dr. Matthiessen, but no result was obtained. 



Aluminium. — When the temperature was so high that the spec- 

 trum of the flame was visible, an absorption was suspected in the 

 violet ; and the appearance did not change on one glass end being 

 removed. 



Zinc. — Many experiments were made on this metal; but there 

 are several points connected with it which require further inves- 

 tigation, and we therefore reserve our remarks on the spectrum 

 of zinc for a future occasion. 



Cadmium. — Under both conditions of thickness the vapour of 

 cadmium gave, in the blue only, an absorption which was very 

 decided ; an absorption in the red was also noticed which had not 

 been observed in previous experiments when a low temperature was 

 employed. 



Manganese. — A small quantity of this metal was prepared with 

 great care by Mr. Bayly, one of the assistant assayers, and it gave 

 a distinct absorption in the red and blue, with evidences of a 

 channelled-space spectrum. In a repetition of the experiment a 

 more distinct channelled-space spectrum was observed. 



Iron. — The metal employed had been obtained by electro-depo- 

 sition in the manner suggested by Mr. Jacobi. Its vapour gave a 

 slight continuous absorption in the blue. 



Cobalt also gave a slight continuous absorption in the blue, but 

 less than in the case of iron. 



Nickel. — This metal behaved in the same manner as cobalt, the 

 absorption being about equal hi amount. 



Chromium. — The amount of metal volatilized was very small, but 

 a fine channelled-space spectrum was observed. 



Tin. — This metal caused a considerable absorption in the blue, 

 but less in the red, no traces of a channelled-space spectrum being 

 visible. 



Antimony. — In results already published it is stated that at the 

 low temperature antimony gives a channelled-space spectrum. In 

 the present experiments we observed merely absorption in the blue ; 

 and this is the only case in which the effects at a high temperature 

 were inferior to those at a low temperature. As the purity of the 

 metal first employed may be doubted, little reliance can be placed 

 on these exceptional results. 



Bismuth. — With the greatest thickness the absorption of bismuth 



