CHAPTER XXI 

 BORING FOR OIL 



CLOSELY similar to coal in chemical matter — ^that 

 is to say, consisting chiefly of definite chemical 

 compounds, called hydrocarbons, built up of only 

 two elements, carbon and hydrogen, and of no others — is 

 a very remarkable class of mineral substances known to 

 the ancients as " bitumen." In its widest sense, it includes 

 " natural gas," the variously mixed liquids called 

 " petroleum " and the solid " asphalts." In ancient times 

 the more fluid kinds of petroleum issuing from the ground 

 in South Russia and Persia were called " naphtha," and 

 that name is still applied to the more volatile hydro- 

 carbons obtained by the distillation of such substances as 

 coal-tar (the residue of the extraction by heat of com- 

 mercial gas from coal), bituminous shale, petroleum, wood 

 and some other bodies which owe their existence to the 

 activity either of living or of long-extinct and " fossilized " 

 plants and animals. 



The bitumens, together with coal, present in their 

 natural state a very large variety of inflammable con- 

 stituents — gaseous, liquid, and solid hydrocarbons; but, 

 when " distilled " at various temperatures and under con- 

 ditions determined by the manufacturing chemist, they 

 yield a still larger series of pure separable bodies, which 

 have been minutely studied and classified according to 

 their chemical constitution. They are produced in great 

 chemical factories in large quantities for use in the most 



