Messrs. Allen and Pepys on the 
in No. XII. of this volume, we were enabled to proceed in this 
respect with great confidence. 
Our object was, to consume certain known quantities of 
diamond and other carbonaceous substances in oxygene gas, 
and we at first determined to employ the sun's rays, by means 
of a powerful lens; but considering the uncertainty of a 
favourable opportunity in this country, and at the season in 
which our experiments were made, we resolved to employ 
the apparatus represented by the drawing. 
Description of the Apparatus. 
This consisted of two mercurial gasometers, fig. 1 and 2, 
each capable of containing from 70 to 80 cubic inches of gas. 
The internal cylinder CC is of cast iron, and solid, except the 
perforation through its middle; the external cylinder is also 
of cast iron ; and the glass receiver slides up and down in the 
space between them, which is filled with mercury: not more 
than sixteen pounds are required for each, and the small bath 
B, fig. 1. 
To the top of each receiver, a graduated scale or register 
H, is screwed, shewing the number of cubic inches of gas, 
measuring from the upper edge of the external iron cylinder. 
The level of the mercury is ascertained by a small glass gauge. 
The registers were graduated by throwing up one cubic inch 
of gas at a time. 
The gasometers stand upon mahogany stools, perforated 
for a socket, to which, according to the nature of the experi- 
ment, a small receiver R, or the triple socket TS, or any 
other combination, may be united. 
P represents the platina tube with its furnance ; the ends 
