ABSTRACTS OF PAPERS 73 



A shale is generally defined as a rock formed by the consolidation of clay, 

 mud, or silt, having a fine laminated or fissile structure. When such a rock 

 contains bituminous or organic matter enough to yield oil, gas, and tar on 

 distillation, it is called oil shale. 



The Chocolate shale of the Devonian of Illinois has formed the basis of this 

 study. The New Albany Black shales of Indiana and the Ohio shales of Ken- 

 tucky vi^ere also studied and closely compared. Shales of other geological 

 formations and from other States and countries were also compared. 



The oil-bearing shales from the Devonian of Illinois, Indiana, and Kentucky 

 are quite similar and what is said of the one is true of the other with but 

 few exceptions. 



The shale is in the main composed of three distinct components : clay, 

 pyrites, and organic matter. These three constituents vary in proportion 

 from place to place and from layer to layer, sometimes in close succession. 

 The clay may be said to form the base in which the other components are 

 imbedded, and generally constitutes the largest proportion. 



The main bulk of the clay consists of very fine grains, but intermixed with 

 this is always a varying percentage of larger crystalline grains. The finely 

 divided clay can not ordinarily be distinguished from the organic matter, even 

 at higher magnification, while the larger grains are easily distinguished at a 

 magnification of from 200 to 1,000 diameters. 



The organic matter consists largely of spores or spore matter, some cuticular 

 matter, and unidentifiable darker-colored organic matter. At a magnification 

 of 200 diameters numerous rather large spores are clearly seen to be imbedded 

 in a mass of light to dark grayish brown color, together with numerous opaque 

 pyrite particles. Several types of these spores are distinguishable. Some of 

 them are probably the spores called Sporangites huronensis by Dawson. 



At a much higher magnification, at 1,000 diameters or over, the organic 

 matter lying between the larger spores is resolved mainly into four kinds of 

 constituents: (1) fragments of the larger spores In all stages of comminution; 

 (2) very small thin-walled spores; (3) cuticular matter in all stages of com- 

 minution, and (4) darker-colored organic matter. 



The smaller spores are very poorly preserved and are recognized with diffi- 

 culty. The darker-colored organic matter is not identifiable, but probably 

 constitutes the degradation matter of various plant tissues and substances. 

 Little or no resinous matter is present. 



Very small globules of pyrites are quite uniformly distributed through the 

 shale. The particles are quite similar to those found in the coals, but are 

 more uniformly distributed, much more numerous, and on the whole smaller 

 in size than those in the coals. 



Samples of oil shale from Scotland were found to be very similar to the 

 Devonian shales of Illinois, Indiana, and Kentucky. Oil shales of the Potts- 

 yille of Kentucky are also similar to these, but contain a larger proportion of 

 organic matter other than spores. 



Presented with the aid of lantern slides. 



Doctor Thiessen's paper was discussed by Dr. David White, but further 

 discussion was postponed to the afternoon session and at 13.30 o'clock 

 recess for luncheon was taken. 



