FOREIGN CURRESPONDENCE. 
203 
simple, that enables him to submit vegetable matters previously eu- 
veloped in damp clay, to an elevation of temperature ranging bet areen 
200 and 300 degrees (Centigrade), and sustained for a long period of 
time. The apparatus is not perfectly or hermetically closed, but 
allows, though with difficulty, the vapour and the different gases to 
escape. In this manner, organised vegetable tissues are decomposed at 
a moderate temperature, and under a sufficient degree of pressure to 
prevent any serious disagregation of their parts. Saw-dust of different 
kinds of wood produces, in this experiment, different varieties of coal; 
and, moreover, stems and leaves print their forms on the clay in a thin 
bituminous, or coaly layer, which gives to the specimens produced the 
aspect of every description of coal-schist on which we observe, in 
nature, similar impressions. 
We must here remark, however, tliat, long before the time of 
M. Barouilier, Hutton used, with many others, to look upon coal as the 
product of a species of dry distillation ; and, to give to his ideas all 
necessary confirmation respecting this, he submitted pieces of wood to 
intense calcination in a hermetically closed iron vessel. He obtained 
in this manner a species of coal, or rather a melted mass of something 
very much resembling coal, but which showed no organic texture 
whatever. But, from the beautiful investigations of MM. Link, 
Ehrenberg, and many miuroscopists, it is next to impossible to find a 
piece of coal which does not evince ample proofs of its organic origin 
by the numerous, and oftentimes perfectly preserved, organised tissues 
it contains. The most important feature in M. Barouilier's experiment 
is, then, the production of coal, preserving, at the same time, its organic 
texture entire. Other experimental philosophers, amongst whom we 
should name Hutton, Petzholdt, Cagniard do la Tour, &c., have pro- 
duced curious varieties of carhon or bitumen, in their experiments — 
M. Barouilier has formed co((l.'^- 
{To be continm'l.) 
In the second volume of the new edition of Mantell's " Wonders of Geology," 
just jiublished, our renders will find an ample rcsurid of microscopical re- 
searches in the structure of coal, aud a notice of the experiments by (ioeppert and 
others, in illustration of the nature of coal. — Ed. Gjsologist. 
s 2 
