Oil Wells Petroleum. 75 



21. These drilling or boring tools are lifted up into a 

 high wooden tower by machinery, and let fall, as rocks are 

 drilled for blasting. (Such a tower you may see in the 

 large chart.) 



22. As soon as the bore enters a seam or channel in 

 which water is confined by surrounding rock or clay, the 

 water is pressed upward through this small opening. The 

 pressure is exerted by the water which lies in these same 

 underground channels and reservoirs on higher ground. 



23. The underground seams serve as great pipes in 

 holding and conducting water to great distances ; and an 

 Artesian well is like a burst in a pipe. 



24. Artesian wells have been bored to depths of hun- 

 dreds and even thousands of feet. By means of them an 

 abundance of water is obtained even in deserts. 



25. It is from such wells as these that the oil 

 called petroleum is obtained, which is used for 

 oiling machinery and for burning in lamps. It 

 is from this that kerosene is now made. 



26. The oil wells of Pennsylvania, Ohio and West 

 Virginia furnish Europe with about fifty million dollars' 

 ($50,000,000) worth of oil every year. 



27. The origin of petroleum or rock-oil is variously 

 attributed to vegetable, animal and mineral substances, 

 which may have sunk, many years ago, below the earth's 

 surface (p. 148). 



28. Some wells yield salt water, from which salt is 

 obtained (pages 17 and 18). Large quantities of salt are 

 thus made in New York, West Virginia and Michigan. 



