274 SCIENCE IN SHORT CHAPTERS. 



and formed a pool which has since been filled up by the 

 debris of the ordinary mine workings. 



A publican in the 'Black Country of South Staffordshire 

 discovered an issue of inflammable vapor in his cellar, col- 

 lected it by thrusting a pipe into the ground, and used it 

 for lighting and warming purposes, as well as an attraction 

 to customers. 



These and other cases that might be cited, although ex- 

 ceptional, are of some value in helping us to form a simple 

 and rational theory of the origin of this important natural 

 product. They prove that mineral oil may be produced in 

 connection with coal seams and apparently from the coal 

 itself. A sound theory of the origin of petroleum is of 

 practical as well as theoretical value, inasmuch as the very 

 practical question of the probable permanency of supply 

 depends entirely on the nature of the origin of that supply. 

 Some very odd theories have been put forth, especially m 

 America. 



Seeing that petroleum is commonly found associated with 

 sandstone and limestone, especially in cavities of the latter, 

 it has been supposed that these minerals somehow produce 

 it. Turning back to the Grocer for April 18, 1872. I 

 find some speculations of this kind quoted from the Pe- 

 troleum Monthly The writer sets aside altogether, as an 

 antiquated and exploded fallacy, the idea that petroleum 

 is produced from coal, and maintains "that petroleum is 

 mainly produced from, or generated through, limestone," 

 and argues that the generation of petroleum by such rocks 

 is a continuous process, from the fact that exhausted Avells 

 have recovered after being abandoned, his explanation being 

 " that the formerly abandoned territory was given up be- 

 cause the machinery for extracting petroleum from the earth 

 exceeded in its power of exhausting the fluid the generative 

 powers by which it is produced ;" these generative powers 

 somehow residing in the limestone and sandstone, but how 

 is not specified. 



Some writers have, however, gone a little further toward 

 answering the question of how limestone may generate 

 petroleum. They have pointed to the fossilized remains of 

 animals, their shells, etc.. existing in the limestone, and 



