486 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



homogeneous, elastic, broken with difficulty, is deep brown and has 

 a resinous luster. The lamination, due to colonies of algae, is often 

 minute and recognizable only on close examination. The " funda- 

 mental matter" contains infiltrations, pyrite, calcite and thelotite, 

 the last being an enriching material, coloring the algae blood-red. 

 Analyses of specimens from two localities show 



Volatile. 



Margenne 65.6 



Thelots 73-75 



Ash. 



34-4 

 26.25 



but these were selected specimens ; ordinarily the ash varies from 

 35 to 48 per cent. The organic matter consists of carbon, 80; hy- 

 drogen, 10; oxygen and nitrogen, 10; the ash from the two localities 

 named contains 



The algae, Pila hihractensis, B. and R., belong to the gelatinous 

 group and are fresh-water forms like the fleurs d'eau. No spores, 

 sporangia, sexual organs or embryos have been discovered. Thtse 

 algae, at times, compose 75.5 per cent, of the whole mass. The 

 " fundamental matter " contains remains of organisms, Pila, fish 

 and grains of pollen; the last being in great abundance, 25,000 to 

 80,000 in a cubic centimeter, indicating showers of pollen. Besides 

 these, are fragments of wood and leaves ; but neither cyprids nor 

 diatoms were observed. 



The deposit is a lens, formed as cannel in a pond as is the organic 

 mud, which so often is foundation for a peat deposit. The reasons 

 for regarding the thelotite, pyrite and calcite as infiltrates are not 

 very clear. Certainly the source of the thelotite was not ascer- 

 tained. If it came from the enclosing bituminous shale, it can 

 hardly be regarded as extraneous. Bertrand and Renault think 

 that the boghead was formed in quiet water with little or no current 

 and they regard the fundamental matter as ulmin which was held in 

 solution. It is quite possible that the lime, present in considerable 

 proportion, would suffice to precipitate the ulmin, but in that case it 



