104 Proceedings of Learned Societies. 
by comparing the spectrum with one of the same metal furnished by the 
use of a lens and prism of rock-crystal. 
ceiaabiestal, however, possesses but a comparatively small refit 
and dispersive power, whilst it almost always affords some trace o ble 
refraction in one portion or other of the spectrum procured by its means. 
to a description of the electric spectra of some of the more im 
nee tary bodies, and the effect of varying the gaseous media in — 
may The —— these spectra are made to originate. 
n the ta action of the different media, the source of light em- 
upon was the electric spark obtained between two metallic wires (gem 
erally of fine silver), connected with the terminals of the secondary wires 
m was received upon a collodion Alin coated: with :iodid: of “—_ 
this supported in the frame of a camera, and after an exposure, general} 
lasting for five minutes, the i ~—” was developed by means of pyr 
acid, and fixed with cyanid of potassium. 
The general results of these experiments were as follows : 
1. Colorless bodies, which are equally — to the y vinibhe my 
= greatly in permeability to the chemical 
es which are photographically eaneparent; in the solid frm, 
"eit their transparency in the liquid and in the gaseous states. 
3. Colorless transparent solids, which exert a considerable hotographia 
absorpti mee preserve their oe _ with greater onl 
both in the liquid and the gaseous 
Whether the compound is Hiquefied by by heat or dissolved in water, these 
usions respecting liquids are equally true. The perfect t permeability 
of water to the chemical rays, conjoined with the circumstance that in no 
instance does the process of solution seem to interfere with the special ac- 
tion upon the incident rays of the substance dissolved, renders coll practica- 
vi j | aki nat bs ple yy rial. 
lass, crown, hard white Bohemian, plate-glass, ‘window-sheet, and 
: Se tedh wide thin arson the spectrum 
