FOREIGN CORRESPONDENCE. 



203 



simple, that enables him to submit vegetable matters previously en- 

 veloped in damp clay, to an elevation of temperature ranging between 

 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, that, 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 microscopists, it is next to impossible to find a 

 piece of coal which docs 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, Petzholdl, Cagniard de la Tour, &c., have pro- 

 duced curious varieties of carbon or bitumen, in their experiments — 

 M. Earouilier has formed coal.'^'- 



■ (^To he continued.) 



* In the second volume of the new edition of Mantell's " Wonders of Geology," 

 just published, our readers will find an ample resume of microscopical re- 

 searches in the structure of coal, and a notice of the experiments by Gfoeppert and 

 others, in illustration of the nature of coal. — Ed. Geologist, 



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