273 ANNALS NEW YORK ACADEMY OF SCIENCES 



fully the composition of the coal. There is notable variation in the seve- 

 ral parts of the bed, Nos. 1, 5 and 6 being from contiguous localities. 

 There seems to have been little change as the result of the abrupt folding ; 

 hence, a series of analyses showing the composition of the coal in each 

 yard from the bottom to the top ought to prove serviceable to the student 

 busied with the origin of coal ; such a series should show variations like 

 those in the Mammoth bed of the Southern Anthracite field. The coals 

 from Miramont, Domergue and Bourran are under cover of the Bourran 

 and Permian deposits; but the coal of Fraysse and Firmy are in locali- 

 ties which must have been freed from most or all of the Permian and 

 perhaps some of the Bourran load during the pre-Jurassic erosion. 



At first glance, one might be tempted to draw some conclusions from 

 the relations of the fuel ratios ; but several ultimate analyses by M. Ney- 

 ron Saint-Julien induce hesitation. These show that the composition is 

 unusual for a Carboniferous coal ; at all events, it is very unlike that of 

 Carboniferous coals in Great Britain and America. The results are : 



Carbon Hydrogen Oxygen and nitrogen 



1. Bourran 63 4 33 



2. Firmy 70 5 25 



3. Miramont ... 69 5 26 



4. Rulhe 70 6 24 



The composition is that of the dry coal in each case. M. Brocard 

 states that a cold solution of caustic potash ordinarily has no effect on 

 the coal, but, most commonly, boiling colors the solution pale yellow to 

 black. This test is employed to determine the coking value of the coal ; 

 when the coloration is brown, the coal gives a poorly consolidated coke. 

 This incidental observation by M. Brocard is evidence that material dif- 

 ferences in composition exist within the bed. Several A^ears ago, Steven- 

 son^ subjected a number of Carboniferous and Cretaceous coals to the 

 caustic potash test and found that those giving a good coke were not 

 attacked even after long boiling, while the open burning were attacked 

 readily. He supposed that he was in the way to discover a convenient 

 mode of determining the value of the coal, but Canadian reports of recent 

 years give numerous instances of coals readily attacked by caustic potash 

 yet yielding strong coke. These coals are closely allied in composition to 

 lignites. The Decazeville coal cokes readily, but the coke is not strong 

 and the burden must not exceed 60 feet. 



The peculiarity of the Bourran coal which at once attracts attention 

 is its tendency to spontaneous combustion. A heap more than six feet 



«J. J. Stevenson, "Jurassic coals of Spltzbergen," Ann. N. Y. Acad. Scl., vol. xvl, 

 p. 90, 1895. 



