366 SCIENCE PROGRESS. 



a considerable amount of information as regards the micro- 

 scopic structure ; he discusses the source and manner of 

 formation of the mineral charcoal (Fusain or Faserkohle), 

 and considers that it has been formed by the breaking up of 

 the woody interiors of many of the flattened hollow stems 

 which are so common in coal and the associated shales. 

 The separation of bark and wood, and the gradual dis- 

 integration of the latter, are phenomena which may be 

 observed in present-day forest trees. 1 In amorphous coal, 

 Grand' Eury considers we have the result of a precipitation 

 of ulmic substances, with spores and other parts of plants on 

 the floor of a lake or sea. In their recent monograph on 

 the fossil plants of the Commentry coal field, Renault and 

 Zeiller devote some pages to the microscopical examination 

 of coal. The cannel coal of Commentry is compared with 

 that from Lancashire ; both consist largely of an amorphous 

 substance, with occasional spores and tissue fragments. 



Anthracite is more difficult to examine, and shows less 

 organic structure. The boghead is rich in inorganic 

 matter, but also contains numerous small lenticular bodies 

 exhibiting fine radiating lines, extending from the centre to 

 the periphery, where they lose themselves in a mass of fine 

 granulations. 2 In ordinary coal portions of carbonised stems 

 of Catamites, Psaronins and other plants are occasionally 

 met with. 



Allusion has already been made to the Scotch torbanite 

 or boghead ; this, with similar carbonaceous beds from 

 Autun and Australia, has recently been the subject of an 

 article by Bertrand, who has previously published some re- 

 searches on the same subject in collaboration with Renault. 

 The bogheads are described as coals which yield, on distilla- 

 tion, a large quantity of very bright gas. Examined micro- 

 scopically they reveal the existence of numerous golden 

 yellow balls possessing a radiate structure ; occasionally 

 there may be as many as two hundred and fifty thousand to 

 one million of these minute spherules in one cubic centi- 

 metre. A close examination of these structures leads 

 Bertrand and Renault to regard them as the thalloid bodies 



1 Solms-Laubach (i), p. 24. 2 Renault and Zeiller, PI. lxxiv., fig. 9. 



