116 THE IRRIGATION AGE. 



gain an appreciation of the time which must have passed since the 

 last disturbance closed the northern gate and walled in the then fresh 

 water lake. Although the area of that period evidently many times 

 exceeded that of modern times, it may be asserted with certainty 

 that Bear and Utah Lakes had by that time become separate from 

 the main body, or were by that convulsion set free. They have re- 

 mained fresh because they have been drained into the Great Salt 

 Lake. Prom the fact that Utah Lake today is but 100 feet above Salt 

 Lake, it is apparent that the larger body has fallen less than that dis- 

 tance since the last of the three great outpourings of its contents. 



The proof that it has been much lowered since then is found in 

 the numerous salt deposits within ten and twenty miles of the shore,, 

 showing that the salt sea once lay above the spots. 



It did not take the lake long to become intensely saline after it 

 was locked in. For its expanse, it was shallow even then, not more 

 than 160 feet deep at its deepest place, probably not that. The maxi- 

 mum depth today is sixty feet, and the average is not half that figure. 

 At some points one may wade a mile and more from shore without 

 getting in water over the knees. It was as if a huge and shallow 

 basin had been spread out in the sun. The ratio of evaporation, far 

 greater than at sea level, hurried the chemical action and in a com- 

 paratively short time the fresh water lake was a salt sea. What may 

 have been the effect of the alkali in the surrounding soil is problemati- 

 cal. Some persons have credited it with being the fundamental cause 

 of the exceptional salinity. 



In the proportion of solid matter in its contents, the Great Salt 

 Lake is surpassed only by the Dead Sea. In the former the ratio is 

 86 parts of water to 14 of solids, in the latter 76 parts of water to 24 of 

 solids. The Atlantic Ocean contains 96.5 parts water to but 3.5 parts 

 solids, emphasizing the abnormal quantity of salt in both the inland 

 reservoirs. 



As the salinity increased tha amount of evaporation increased, 

 and it is likely enough that to this cause alone the lake owed the 

 gradual fall which brought it down to an area of 1,700 square miles 

 seventy-five miles long and between twenty-five and thirty miles 

 broad its surface during the earlier half of the present century and 

 at the time the Mormons came into the Jordan Valley. 



' About 1850 the lake began to rise, reaching in a few years the 

 area of 2,360 square miles, which it retained until 1870, when irriga- 

 tion ceased to be desultory and became a system. The lake's rise has 

 given rise to much discussion, and furnished some excuse for the infer- 

 ence of a hidden feeding stream. In general the phenomenon is laid to a 

 series of unusually wet seasons, which not only increased the volume 

 of the streams emptying into the lake but also did away with the 

 necessity of irrigation. 



Since 1^70 irrigation has been taking yearly more and more of the 



