P OP ULAR MIS CELL AN Y. 



2 53 



slate, and shale; but the second of these 

 three members the Mahoning sandstone 

 is the principal repository of petroleum in 

 the southwestern district. The " oil-sands " 

 of the western district are also three in 

 number. The first sand of this group yields 

 a heavy lubricating oil, 30 to 35 gravity ; 

 the second, an oil about 40 gravity; the 

 third, a light oil, 45 to 50 gravity. This 

 third sand is the most productive, and sup- 

 plies most of the oil of commerce. The 

 " Warren oil-sand " of the northern district 

 is very irregular in character, and the oil is 

 found at horizons varying from 600 to 800 

 feet below the " third sand " of the preced- 

 ing group, whose oil it, moreover, resembles. 

 But at a depth of about 300 feet below the 

 Warren horizon, and in the same northern 

 district, is the Bradford oil-belt of McKean 

 County, Pennsylvania, and Cattaraugus 

 County, New York, the surest and safest 

 oil-territory in all the oil-regions. The oil 

 of the Bradford belt is of the same gravity 

 as " third-sand oil." 



The Ancient Beaches of Great Salt Lake. 



The mountains round about Great Salt 

 Lake bear plain evidences of the existence 

 at some early period of a much larger lake 

 in the same locality. The sides of these 

 mountains rise, as it were by steps, to the 

 height of 1,000 feet above the surface of 

 the present lake, these steps marking the 

 successive levels of the lake as it shrunk 

 from its primeval dimensions 345 miles 

 long, 135 miles broad to the size it now 

 possesses. Mr. G. K. Gilbert, of Powell's 

 Survey, has made a very thorough study of 

 these ancient beaches, and publishes an arti- 

 cle on the subject in a recent number of the 

 American Journal of Science. This ancient 

 lake has received from geologists the name 

 of Lake Bonneville, and the great problem 

 was, to discover the outlet through which 

 its waters were drained away. To this end 

 it was necessary to find a point where the 

 Bonneville shore-line was interrupted by a 

 pass of which the floor was lower than the 

 shore-line, and which led to a valley not 

 marked by a continuation of the shore-line. 

 These conditions are satisfied at Red Rock 

 Pass, and, in addition, there is a continuous 

 descent from the pass to the Pacific Ocean. 

 All about Cache Valley the Bonneville shore- 



line has been traced, and it is well marked 

 within a half-mile of the pass. The floor 

 of the pass at the divide is 340 feet below 

 the level of the shore-line, and its form is 

 that of a river-channel. The gentle alluvial 

 slopes from the mountains at the east and 

 west, which appear once to have united at 

 the pass, are divided for several miles by a 

 steep-sided, flat-bottomed, trench-like pas- 

 sage, 1,000 feet broad, and descending north- 

 ward from the divide. At the divide Marsh 

 Creek enters the old channel from the east, 

 and, turning northward, runs through Marsh 

 Valley to the Portneuf River, a tributary of 

 the Columbia. In Marsh Valley the eye 

 seeks in vain for the familiar shore-lines of 

 the Salt Lake Basin, and the conclusion is 

 irresistible that here the ancient lake out- 

 flowed. On the sides of the mountains, 

 from the highest shore-line, known as the 

 ' Bonneville Beach,' down to the level of the 

 modern lake, there is a continuous series of 

 wave-wrought terraces recording the slow re- 

 cession of the water. As many as twenty-five 

 have been counted on a single slope. Some 

 are strongly marked and others faintly, and 

 some that are conspicuous at one point fail 

 to appear at other points ; but there is one 

 that under all circumstances asserts its su- 

 premacy and clearly marks the longest lin- 

 gering of the water the ' Provo Beach,' 

 which runs about 3&5 feet below the Bonne- 

 ville Beach. When the discharge of the 

 lake began, its level was that recorded by 

 the Bonneville Beach. The outflowing stream 

 crossed the unconsolidated gravels that 

 overlay the limestone at Red Rock, and cut 

 them away rapidly. The lake-surface was 

 lowered with comparative rapidity until the 

 limestone was exposed, and thenceforward 

 the process was exceedingly slow. For a 

 long period the water was held at nearly the 

 same level, and the Provo Beach was pro- 

 duced. Then came the drying of the cli 

 mate, and the outflow ceased ; and slowly 

 the lake has since shrunk to its present size. 



Discolored Sea-Water. While engaged 

 in a survey of the Gulf of California the 

 Mar Vermijo, or Vermilion Sea of the early 

 Spanish navigators Surgeon T. H. Streets, 

 of the navy, examined some of the water in 

 order to ascertain the cause of the peculiar 

 coloration. This red color occurs in patches, 



