COAL: ITS STRUCTURE AND FORMATION. 363 



of the Scotch boghead or torbanite, a substance rendered 

 famous by the legal proceedings in the case of Gillespie v. 

 Russel, 1 and by the scientific evidence of experts in favour of 

 and against its close connection with coal. Bennett figures 

 some sections of ordinary coal showing crushed resinous 

 spores, also sections of the boghead containing numerous 

 transparent bodies of irregular outline, embedded in a black 

 matrix. The bituminous boghead is considered to be 

 essentially distinct from coal in the absence of obvious plant 

 structures. Bertrand and Renault, 2 who have lately ex- 

 amined the Scotch boghead, give an entirely different 

 interpretation to the yellow bituminous bodies of Bennett 

 and others ; they look upon them as the well-preserved 

 remains of fresh-water algae. 



Balfour dissents from Bennett's views as to the nature 

 of boghead, and prefers to class it with true coals ; his paper 

 on this subject contains a figure of an interesting example of 

 " spore " coal. 



Without attempting to give any complete account of the 

 earlier contributions to our knowledge of coal structure, such 

 as those by Quekett, Phillips, and others, a brief reference 

 may be made to Huxley's description of what he regarded 

 as sporangia and spores in the well-known Better bed coal 

 of Bradford. Williamson 3 pointed out the fact that the so- 

 called sporangia were macrospores, and the smaller bodies 

 microspores ; this palseobotanist gave a short preliminary 

 account at the York meeting of the British Association in 

 1 88 1 of his researches on the structure and physical com- 

 position of coal. For several years the task, which Professor 

 Williamson set himself, of making a " systematic series of 

 microscopical observations on the coals of the entire world," 

 has been gradually proceeded with ; and the publication of 

 these researches should put us in possession of many impor- 

 tant data, from which we may expect to obtain further light 

 on the question of coal formation. 



1 An account of the evidence given at this trial by scientific experts 

 will be found in Quekett's paper. 



2 See references given in Bertrand's paper, also " Science Progress," 

 vol. i., p. 60. 3 Williamson (2). 



