POOLE ON THE GREAT AMERICAN DESERT. 215 



hard to contemplate what physical changes must have taken place 

 in the adjacent regions of the continent since the earlier days of the 

 present epoch when this immense lake existed, so to affect the 

 climate of a country which for a lengthened period undoubtedly 

 was humid, but is now arid for at least the greater part of the year. 

 It is evident that for countless ages this great inland sea 

 existed, and receiving the detritus washed from the shores of 

 the numerous chains of islands studding its surface, distributed 

 it according to the size of the particles in the valleys adjacent ; 

 carrying the fine sediment to the centre of the valleys, and leaving 

 on its shores the coarser material to form the gravel benches which 

 now belt the mountain ranges. The thickness of these deposits is 

 as yet undetermined. The deepest wells yet sunk have only reach- 

 ed a depth of two hundred feet, and merely show that the materials 

 composing the benches are not all uniform in size. Beds of 

 coarse gravel give place and alternate with beds of fine gravel and 

 sand. Here and there through the deposit, boulders of stone record 

 the existence of ice at times in the days of this ancient lake. The 

 action of ice, probably in the form of glaciers, is also recorded in 

 the well rounded stones found in the gravels of the most elevated 

 valleys, which stones have been fractured and re-cemented together, 

 as are those of a similar character found in the terminal moraines 

 of existing glaciers. From the great width of the main valleys and 

 the precipitous sides of the mountain ranges, I have little doubt 

 but that the bottoms of the valleys were originally much below 

 their present position, and that they have been filled in with detrital 

 matter to the depth of many hundreds, if not thousands of feet. 



An apparent further confirmation uf the great altitude which the 

 surface of the lake attained in former times is to be seen at Binsf- 

 ham Canon on the east side of the Oquirrh Mountains, where at a 

 height of 300 feet above the present bed of the canon and close to 

 the town, a portion of the old bed remains on the side of the 

 mountain. This bed had a steep descent towards the plain, and jet 

 became choked with great water worn boulders of the country 

 rock. In the clay and with the fragments of Cjuartz veins wdiich 

 fill the interstices between the boulders much of the gold which 

 gives Bingham its celebrity as a mining camp, is found. It is 



