GEOGRAPHY OF NORTH AMERICA. 215 



the Kocky Mountain region itself, at stations connected by 

 careful levelling, both with each other and a determined 

 base. Those now in use are founded on observations at 

 somewhat distant points in Switzerland, under climatic con- 

 ditions greatly different from those obtaining in the Kocky 

 Mountains. Such a series of observations, however, would 

 need to extend over long periods to attain the desired re- 

 sult. 



Besides the three parties mentioned, separate geological 

 investigations were carried on in other parts of Utah by Mr. 

 Gilbert and by a party under Captain Dutton. The classi- 

 fication of lands occupied much of their attention. Mr. Gil- 

 bert traversed that portion of the drainage basin of Great 

 Salt Lake which lies in Utah : it includes within its limits 

 the most valuable land of the territorv, as well as some of 

 the most sterile, where the possibility of agriculture depends 

 on the possibility of irrigation. By measuring the volumes 

 of the streams, an attempt was made to ascertain the agri- 

 cultural capabilities of the river valleys. Some of the smaller 

 ones proved inadequate to serve the lands, otherwise arable, 

 through which they run. East of the lake more than twelve 

 per cent, of the district is reclaimable ; while west of it only 

 a fourth of one per cent, is of value for farming. It is also 

 estimated that about two and one third per cent, of the whole 

 territory of Utah can be redeemed by the utilization of the 

 streams, but without the construction of reservoirs ; and that 

 one third part of the irrigable lands of the Salt Lake basin is 

 now under cultivation. 



An investigation was also made of the climate of the dis- 

 trict, as recorded in the rise and fall of Great Salt Lake. 

 Until recently, no systematic record of its fluctuations has 

 been kept ; but from inquiry among the settlers it appears 

 that the water is now much higher than formerly. From 

 1847 to 1850 it was low; then for five years it rose at about 

 the rate of one foot per annum, afterwards fell to its original 

 level (in 1861-62), and then continued to rise until 1868, 

 when it reached its present height ten feet above that first 

 observed which, with slight fluctuations, it has maintained 

 ever since. Since the area of the lake is much greater with 

 this increased altitude, and the loss by evaporation corre- 

 spondingly increased, the inflowing water must be one tenth 



