Ingredients in Banded Bituminous Coal. 471 



the course of the joint researches Dr. E. V. Wheeler and I have been follow- 

 ing out on various other aspects of the hydra-headed " coal-problem." 



In this paper the only type of coal dealt with is British palaeozoic (Coal 

 Measure) streaky bituminous coal, the kind of coal which every household 

 and most factories employ. The appearances of the microscopic section'' of 

 Cannels, Bogheads, Anthracites, and " Lignites " are each distinctive a.id 

 significant, but they are not dealt with at all in the present paper. 



The actual coal chiefly used in the research was the various bands of the 

 Hamstead Colliery (Birmingham), and to Mr. L. Holland, the manager, and 

 the Company, I am much indebted for facilities to collect the coal myself in 

 situ, and for various courtesies ; also to Mr. P. S. Lea I am indebted for 

 carefully selected samples from the " Eight-feet seam " from West Cannock 

 Colliery, S. Staffordshire. The observations were checked and supplemented 

 by the examination of various other bituminous coals from widely separated 

 localities. 



In their text-book on the Petrology of Sedimentary Eocks, Hatch and 

 Eastall (1913) describe ordinary coal as follows : " The humic or bituminous 

 group includes the ordinary house, cooking, and steam coals, of which the 

 appearance is so familiar as scarcely to need description. As a rule, they 

 consist of a series of alternating bright and dull layers ; in the latter only 

 can remains of vegetable tissues sometimes be seen." 



This may be taken as summarising a prevalent view ; but, as will be 

 seen on reference to p. 484 below, a conflict of opinion exists about the 

 presence of plant tissues in the " dull " or the " bright " layers ; some of the 

 leading authors taking a view opposite to that of Hatch and Eastall, and 

 stating that it is only in the " bright " layers that tissues are to be seen. 



Preliminary Statement of the Present Contribution. 



Essentially the present contribution to the subject consists in the explicit 

 recognition not of mere " dull " and " bright " bands, but of four distinctive 

 and visibly differing portions forming the mass of an ordinary bituminous 

 coal ; and the demonstration of the fact that these four portions can be 

 recognised and separated from each other both macroscopically, by hand, and 

 microscopically in thin sections ; and that, further, these four portions react 

 so differently to certain simple chemical treatments as to indicate that 

 their chemical molecules should be substantially different from each other. 

 Diagrams of these points, and of the relations of the four constituents to 

 each other in an ordinary sample, as well as colour illustrations of the same 

 in thin sections, are given, 



2 p 2 



