274 PROCEEDINGS OF THE AMERICAN ACADEMY. 



ject are as follows: C. E. Bertrand, Reinschia australis et Premieres 

 Remarques sur le Kt^rosene Shale de la Nouvelle Galles du Sud ; ^ C. 

 E. Bertrand, Les Charbons Humiques et les Charbons de Purins;^ 

 B. Renault, Sur Quelques Organismes des Combustibles Fossiles.^ 

 The contribution of Renault last cited is monumental in its character, 

 representing as it does the labor of nearly a quarter of a century and 

 dealing with most of the kinds of coal, which show structure when ex- 

 amined microscopically. Renault published from time to time, in the 

 Bulletins of the Museum at Paris, his views as to the microscopic 

 structure and related qualities of coal. Bertrand has recently written 

 a very clear popular account of the views of Renault and himself^ 



The ideas as to the constitution of certain coals cited above have not 

 remained confined to their country of origin but have been adopted to a 

 considerable degree in Europe and even in America. Professor Potonie, 

 of the Royal School of Mines in Berlin, has taken up the Renault- 

 Bertrand hypothesis and elaborated it in a number of publications. 

 His views as to the origin of coal are stated with sufficient fulness in 

 a pamphlet which has been of such general interest that it has gone 

 through a number of editions."^ Professor Potonie not only adopts the 

 views as to the origin of boghead coals, oil-shales and bituminous 

 schists advocated by the French authors cited above, but extends 

 them to cannel coal, which Bertrand and Renault in common with 

 other investigators have regarded as composed of the compressed re- 

 mains of the spores of vascular cryptogams. The German author has 

 gone further too than the French in describing recent peats which he 

 supposes to be of algal origin and thus comparable with the bogheads 

 and oil-shales of older geological periods. Dr. Davis White of the 

 United States' Geological Survey has given not long since an admir- 

 ably lucid account of recent views as to the origin of the various types 

 of coal, including bogheads and oil-shales. 



The present writer was led to investigate the subject of bogheads, 

 oil-shales and other supposedly algal coals by reading the article of 

 Dr. White cited above. In the investigations here described methods 



3 Bulletin de la Societe, Hist. Nat. Autun, 1894. 



* Travaux et Mem., Universite de Lille, 6, Memoir 21, 1S98. 



^ Bulletin de la Soci6t6 de I'lndustrie Mincrale, Serie 3, Tome 13, 4me. 

 Livraison, 1899; Tome 14, Ire. Livraison, 1900, with atlas of 30 folio plate 

 containing a large number of photomicrographs. 



^ Notions Nouvelles sur la Formation des Charbons de Terrc, Revue du 

 Mois, 3, No. 15, pp. 323-41, Paris, 1907. 



' H. Potonie, Die Entstehung der Steinkohle u. verwandter Bildungcn 

 cinschliesslich des Petroleums. Vierte verbesscrte u. erweiterte Auflage, Berlin, 

 1907. 



