74 SCIENCE PROGRESS 



tively, afford an interesting constellation throwing light on 

 that most important but little known theme, the structure of 

 coal. 



The first of these papers, that by White and Thiessen, 

 appears to have suffered shipwreck on its way to this country, 

 for several of the chief geological libraries have not received 

 their copies. This is particularly unfortunate, for there is no 

 doubt that it is the most important and the most interesting 

 paper on coal which has appeared for some time. It is remark- 

 able in that it attempts to treat the subject of the origin of 

 coal, not from one side only, but from every point of view. 

 The main headings of the contents table indicate this — there 

 the sections of the work are grouped under the following 

 sub-titles : " Geological Relations of the Coals " ; "Analyses of 

 the Coal Samples Studied " ; " Physiographic Conditions attend- 

 ing the Formation of Coal " ; " Regional Metamorphism of 

 Coal " ; " Origin and Formation of Peat " ; " Microscopic 

 Study of Coal." The contents table alone occupies three and a 

 half pages under the last heading — more than is allotted to 

 the whole subject by most writers on coal. In the prepara- 

 tion of this monograph the work of section cutting and pre- 

 paratory technique occupied several years, and the Bureau 

 of Mines appointed Dr. Thiessen specially for the microscopic 

 examination of the coals. The results, though far from ex- 

 hausting the subject, indicate what might be done with adequate 

 facilities. One result of Dr. Thiessen 's work, a result of per- 

 manent value, is the final explosion of the myth of " algal 

 coals," which were supposed to be formed by a special organism 

 " Pila." Different species of this supposed peculiar organism 

 have been described from boghead coals, oil shales, etc., and 

 their algal origin was widely believed in. This myth got a 

 good start by being backed by the two distinguished French 

 palaeobotanists, Bertrand and Renault. It went the round of 

 the profession, and is still accepted by most geologists as 

 orthodox. A few years ago Prof. Jeffrey of Harvard brought 

 forward strong evidence against it, and though at that time 

 David White accepted the view, the work he inaugurated with 

 Thiessen converted him to the opinion which will certainly 

 in future be the orthodox one — viz. that these so-called algae, 

 with their peculiar coal-forming habits, were not algae at all, 

 but were partly decomposed Lycopodinean macrospores. 



