144 THE CHEMISTRY OF CREATION. 



to be, as it were, distilled, by a very slow process, 

 into the layers of earth lying just above them, 

 where this substance is generally found. 



In a coal pit near Alfreton, in Derbyshire, a 

 valuable spring of mineral oil has very recently 

 made its appearance. The quantity thrown up 

 varies from 150 to 30 gallons a-day. The pit in 

 which the spring occurs is said to be the deepest 

 in that part of the country. Some years since, 

 a large spring of salt-water appeared in the same 

 pit, and has since flowed uninterruptedly. The 

 spring of mineral oil has accompanied the salt 

 spring since its appearance. The oil as it issues 

 is of a dark tarry colour ; but, on being distilled, 

 yields a volatile liquid, which has been used as 

 a substitute for ether and chloroform in the 

 painless method of operating ; and also a nearly 

 colourless oil, which forms a very valuable 

 source of light when used in a proper lamp. It 

 appears probable that this mineral oil may be- 

 come useful for the purposes of illumination. 

 Mr. Mansfield has proposed an apparatus for 

 impregnating atmospheric air with the vapour 

 of one of the products of distillation of mineral 

 oils, so as to produce, simply by passing Jt'ne . air 

 through the liquid, an illuminating gas. -Mijie- 

 ral oil springs are found in great abundance on 

 the north-west shores of the Caspian Sea, on 

 sinking wells to the depth of about thirty feet, 



