NATURAL HISTORY SOCIETY OF GLASGOW. 135 



These Entomostracan oil shales, if we might so term them, are 

 found principally in the lower coal measures, and carboniferous 

 limestone series, and are often unassociated with any beds of coal. 

 Their range extends from the horizon of the Burdiehouse lime- 

 stone to the top of the lower limestone; they vary in thickness 

 from a few inches to one or two feet; but in the West Calder 

 district, where they are best developed, the beds are not all of 

 one quality, there being layers of the shale less rich in oil than 

 others. 



The idea is not new to geologists that many beds of strata in 

 other portions of the earth's crust, owe the bituminous ingredients 

 with which they are now impregnated, to the various animal organ- 

 isms that have died over those tracts during the formation of the 

 beds. It is also well known that there are strata aboutiding in 

 organic remains which now contain no oil, nor other bituminous 

 ingredients — but these may have escaped from the strata by the 

 action of heat, or otherwise, leaving us nothing to testify to their 

 former abundance but their hard skeletons. It is surprising, how- 

 ever, to note how many strata in our carboniferous system still 

 retain a portion of the organic substances by which they were once 

 impregnated, many of the limestones being quite foetid from this 

 cause ; and from their odour on being struck, or breathed upon, 

 are termed swine-stones, or stink-stones. 



The only Entomostracan oil shale that I know of in the neigh- 

 bourhood of Glasgow, occurs on the south hill at Campsie, in the 

 Hosie limestone series. There are two bands, varying from three 

 to six inches in thickness, yielding, by distillation, from twenty to 

 thirty gallons of oil to the ton of shale. The shale is of a very 

 tough durable character, and was formerly worked near Craigen 

 Glen, in connection with some clay-band ironstone. After the 

 volatile matter is burned out of it, the residue yields some 50 per 

 cent, of lime, and is found to consist of the minute calcareous tests 

 or shells of the Eniomostraca, felted closely together, the species of 

 which the bands are composed being Cijthere fabulina, C. ])ungens, 

 and C. secans. They also occur in some of the limestone strata of 

 that district. 



I have in the foregoing remarks indicated what appears to me 

 to be two distinct varieties of oil shales — vegetable and animal. 

 Those of animal origin are said to yield an oil of lighter specific 

 gravity than that found in the vegetable oil shales, or cannel coals, 



