226 SECRETS OF EARTH AND SEA 



drilling had been carried to a depth of 6g ft. the tools 

 suddenly dropped into a subterranean cavity, and on the 

 following day the well was found to have " struck oil," and 

 twenty-five barrels a day were yielded by that well for 

 some time. From here the industry spread over the 

 States and Canada, and in 1908 the year's yield was 

 45,000,000 barrels. 



Since 1870 the industry has spread all over the globe — 

 Russia, Galicia, Rumania, Java. Borneo and Burma being 

 prominent sources of the oil supply of the world. The 

 raw petroleum of different localities differs in each case in 

 the amount of solid paraffins and olefines dissolved in the 

 liquid paraffins. Other substances also are dissolved in it 

 in variable amount — such as benzene, acetylene, camphene 

 and naphthalene. The fact that the oil, when reached by 

 a boring, is often found to be under a considerable 

 pressure, so that it rises and flows from the surface of the 

 well, or even may shoot up as a great fountain, is an 

 important feature in the oil-seeking industry, though the 

 supply depends largely on pumping and not necessarily 

 on natural flow. The borings when made, act like Artesian 

 wells, and sometimes are carried to a great depth. Those 

 in Pennsylvania vary in depth from 300 ft. to 3700 ft, 

 according to the distance below the surface at which the 

 oil-bearing strata (usually a sandstone) is situate. As in 

 the case of an Artesian well, the boring is in the first 

 instance an exploration subject to uncertainty as to 

 " striking " the desired liquid, but the uncertainty is 

 greater in the case of the search for oil than in that for 

 water. The water-well is also far less likely to " give 

 out " when once flowing than is that bored for oil, 

 which, even if at first successful, may be soon exhausted 

 owing to the small area of the oil-bearing strata tapped. 

 A cause of the high pressure in many oil-wells is the gas 

 which accompanies the oil. The pressure may amount to 



