Geological Gleanings. 187 



paper on the Blow-pipe Assaying of Coals. The precise differ- 

 ences in the composition of coals have been too much neglected 

 by geological observers ; and a considerable amount of experience 

 in assays and other examinations of this mineral, enables us to 

 say that the methods recommended by Prof. Chapman will be 

 found exceedingly valuable in circumstances in which trials on a 

 larger scale cannot be made. We copy, for the benefit of students 

 of this subject, Prof. Chapman's preliminary classification of the 

 coals : — 



" Without attending to minor distinctions or points of merely 

 local value, we may arrange all varieties of coal, so far as regards 

 practical purposes, under the following sub-divisions : 



1. Anthracites. 



2. Anthracitic or Dry Coals. 



3. Caking or Fat Coals. 



4. Cannel or Gas Coals. 



5. Brown Coals or Lignites. 



These varieties pass by almost insensible transitions into one 

 another. Thus, the cannel coals are related to the lignites by the 

 different kinds of jet, some of which are referable to the one, and 

 some to the other sub-division. Between the caking and the can- 

 nel coals there are also various links ; whilst the anthracite or dry 

 coals, on the other hand — passing by excess of bitumen into the 

 caking coals, and by a diminution of bituminous matter into the 

 anthracites — serve to connect the first and third divisions. The 

 typical or normal specimens of each of these five varieties, how- 

 ever, are sufficiently well marked. 



1. Anthracites. — The true or normal anthracites possess a bril- 

 liant sub-metallic lustre, a degree of hardness varying from 3.0 to 

 3.25*, and a specific gravity of at least 1.33. A specimen from 

 Pennsylvania gave 1.51 ; another specimen, 1.44 ; one from the 

 department of the Isere in France, 1.56 ; and three from Wales 

 yielded respectively 1.33, 1.37, 1.34. It should be stated, how- 

 ever, that many of the Welsh specimens belong strictly to the 

 division of anthracitic coals, rather than to that of the true anthra- 

 cites. The normal anthracites exhibit also a black or grayish- 

 black streak ; and all are good conductors of electricity. The 



* Hausmann in his Handbuch der Minera'.ogie, gives 2.5 as the extreme 

 hardness of all coals ; but this is evidently erroneous, as many speci- 

 mens, not only of anthracite, but of common and cannel coals, scratch 

 calcareous spar. 



