THE NATIONAL GEOGRAPHIC MAGAZINE 



197 



Photograph from U. S. Geological Survey 

 IN THESE WYOMING ROCKS ARE LOCKED MILLIONS OE BARRELS OE OIL 



These deposits of oily rock are often massive in extent as well as in thickness. Beds were 

 recently reported in one Western State over an area of 1,500 square miles, averaging 20 

 feet in thickness and yielding at least 36 gallons to the ton. 



even as low as 20 gallons of oil a ton is 

 yielding good dividends. The shales in 

 the western United States are far richer 

 in oil than those of Scotland. Many tests 

 made by the Geological Survey show that 

 the American rocks contain 40 to 50 

 gallons to the ton and those in one de- 

 posit tested 90 gallons, or more than 2 

 barrels, to the ton. 



To extract the oil, the rock is distilled 

 at a low temperature. So simple is the 

 process that the geologists who surveyed 

 the fields carried small testing retorts 

 around from place to place to determine 

 the oil content of various specimens. 



In the Scotch plants the rock is heated 

 in retorts arranged in banks of four over 

 a single fire-box, and a unique feature of 

 the process is that the gas derived from 

 the shale is the fuel used for obtaining 

 the oil and other products. The retorts 

 are grouped in benches of 64 and each 

 retort reduces about 4 tons of rock a day. 



Some 3,000,000 tons are treated annually. 

 The vapors pass from the retorts into 

 condensers in which the crude oil is de- 

 posited, and then on into a chamber in 

 which the ammonia is collected. 



The Scotch shales yield gasoline, illumi- 

 nating, lubricating, and other oils, paraf- 

 fine wax, and sulphate of ammonia, be- 

 sides a considerable quantity of liquid 

 fuel and the gas that is used in the plants. 



QUANTITY OE OIL IN AMERICAN SHALES 

 ENORMOUS 



The total production of petroleum in 

 the United States up to 191 8 has been 

 4,255,000,000 barrels, and the possible fu- 

 ture production, or the total reserve in 

 the ground — and some of it lies very 

 deep — is estimated by the Federal Gov- 

 ernment at about 7,000,000,000 barrels. 



How does this petroleum compare with 

 the known oil-shale reserve ? The quan- 

 tity of oil that can be extracted from the 



