192 Scientific Intelligence. 
heat to ether ^ alcohol, or water, in the other end. In this way, 
by the pressure of the vapour of ether, he prussic gas y 
and sulphureous acid gas. When these gases were reproduced 
they occasioned cold. — See Phil. Trans. 1823, p. 203. 
22. On the Expansion cfi Gases of dififerent densities hy Heat. 
— In order to determine the law of expansion of gases of different 
densities. Sir H. Davy included dry atmospherical air in a tube 
of mercury, and having raised its temperature from 32° Fahr. 
to 212°, he marked its expansion. The same volume of air, 
but of double and of more, than triple the density under a pres- 
sure of 30° and 65 inches of mercury, were heated in the same 
manner and in the same tubes, and when the necessary correc- 
tions were made for the difference of pressure of the removed 
columns of mercury, it was found that the expansions were 
exactly the same. Sir Humphry next constructed an appara- 
tus, in which the expansion of rare air confined by columns of 
mercury were examined and compared with the expansion of 
equal volumes of air under common pressure ; and he found, 
that, for an equal number of degrees of Fahrenheit’s scale, 
and between 32° and 212°, the expansions were precisely equal, 
whether the air was one-half , one-third, or one-sixth of its natu- 
ral density. Similar results were obtained with air condensed 
six, and expanded ff teen, times. — Phil. Trans. 1823, p. 205. 
23. On Bitumen in Stone. — The Right Honourable George 
Knox, whose experiments on the subject we slightly noticed in 
our last, has subjected various minerals to distillation, for the 
purpose of obtaining their volatile ingredients. He obtained 
(2 per cent, of Bitumen. 
From Arran Pitchstone, - | 2.5 of Water. 
Pearlstone, - - 2.5 Do. and floating Bitumen. 
Basaltic Greenstone, - 1-75 Pure Bitumen. 
Amygdaloid, - - 3.1 Bituminous Water. 
( 11.42 Do., 4 cubic inches of Carbonic Acid, 
Wacke from Disco Island, ^ carburetted Hydrogen. 
Iron-clay from Howth, - 4 Bitumen. 
Hornblende, - - 0.75 Bituminous Water. 
Tourmaline, - - 0.7 Ditto. 
Augite, - - 0.35 Bitumen. 
Serpentine, - - 10.5 Bituminous Water. 
Clay-slate, - - 3.0 Ditto. 
While Felspar, - - 0.35 Ditto. 
