150 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



Lymncca and Planorbis; (7) first lignite, friable and of inferior 

 quality, often has Lymncca and Planorbis in top portion, 0.50 to i 

 meter; (8) blackish carbonaceous shale, with river shells and kidneys 

 of freshwater limestone; (9) second lignite, better than the first, but 

 more irregular, o to 0.50 meter; (10) blackish carbonaceous shale 

 with freshwater limestone, holding Unio, Lymncca and Planorbis; 

 ill) freshwater limestone, with more or less of lignite, 10 to 15 

 meters; (12) third lignite, very irregular, rarely thick enough to be 

 mined; (13) irregular freshwater limestone resting on the nummulitic 

 limestone. 



Unio and Cyclas occur, though somewhat rarely, in the Caunnette 

 lignite. Near the village of Songragnes, de Serres found lignites 

 of apparently the same age, associated with blackish, bituminous 

 marls, which contain much pyrite and some jet. The lignite en- 

 closes many nodules of amber, at times as large as a hen's Qgg. Some 

 are translucent, others opaque, but all yield succinic acid. The note- 

 worthy feature is the mass of freshwater limestone, with minimum 

 thickness of 250 feet and interrupted only by freshwater carbonaceous 

 shale with lenses of brown coal. 



The Eocene Coals. — Molengraaff-^^ has shown that coal-forming 

 conditions existed in central Borneo during the Eocene. The coal is 

 thin at most localities but occasionally it is of workable thickness. 

 One exposure on the Mandai River has a bed, one meter thick, 

 enclosed in shale and rich in carbonized tree trunks, which are partly 

 silicified. Clayey layers of an overlying sandstone contain many 

 impressions of leaves. On the Tabaoeng River, he saw a bed in 

 three benches, 4, 1.40 and 2 meters respectively, separated by thin 

 partings of shale and clayey sandstone, in which are concretions 

 with plant imprints. The lower benches are fissile and evidently of 

 poor quality, but the top bench consists of black pitch-coal, which 

 seems to be good. These localities are within one third of a degree 

 north and south from the equator. The sandstones of this coal- 

 bearing group, not more than 40 meters thick, have grains of coal at 

 many places and the associated volcanic tuffs, of undetermined age, 



208 G. A. F. Molengraaff, " Geological Explorations in Central Borneo," 

 1902, pp. 59, 60, 93. 



