GEOLOGICAL SUEYEY OF THE TEERITORIES. 235 



of wliicli tlie bottom of the lake is composed also probably lias influence 

 in this matter. 



According to my calculation, from all the datal have at hand, the snr- 

 face-area of the lake is about one thousand nine hundred square miles 

 Comparing this with some approximate estimates I have made of the vol 

 ume of water in the principal streams emptying into it, I do not think 

 the entire flow for twenty-four hours, if there was no evaporation, would 

 raise the surface more than one-fiftieth part of an inch, even when at 

 the usual spring standard. In the summer this would not amount to 

 more than one-hundredth part of an inch. Tliat the evaporating power 

 of the atmosphere is far in excess of this amount of water in the sum- 

 mer time is evident to any one who has observed the rapidity with 

 which shallow pools are dried up. The instrumental test, so far as it 

 has been made, shows the atmosphere in summer to be exceedingly dry. 

 While encamped on the margin of Bear Eiver Bay, June 10 to 13, Mr. 

 Schonborn found the difference between the wet and dry bulb to be from 

 24P to 280. The imperfect record of the wet bulb in Captain Stansbury's 

 report does not show this difference, but his observations do not extend 

 into the summer months, reaching only to April 19. Imperfect as this 

 record is, it reveals one important fact, that during the winter months 

 the difference between the wet and dry bulb is very small, not exceed- 

 ing four or five degrees, but gradually increases as the season advances j 

 the greatest difference given being 17^. 



UTAH LAKE. 



This beautiful sheet of pure, fresh water is triangular, its three sides 

 closely margined by mountains. Its base, which is the western side, 

 extends from the exit of the Jordan to the southern extremity of the 

 lake, and is about twenty-two miles in a direct line. Its apex i)oints 

 eastward and extends into the somewhat abrupt bend of the Wahsatch 

 Eange at this point. A direct line from the apex, near Provo City, to 

 the base, is about twelve or fourteen miles. The inclosing sides of this 

 angle are about equal in length, each being some sixteen or seventeen 

 miles direct.* Its surface area isi^robably about one hundred and 

 thirty square miles. Although the Jordan during the spring and first 

 summer months sends down a considerable volume of water, I am satis- 

 fied that it is much less than the amount received by the lake. But as 

 I visited it in the early part of autumn I can speak positively only as 

 to that season of the year. From the observations then made I am 

 decidedly of the opinion that the Provo Eiver alone brought in more 

 water than the Jordan carried off', leaving this surplus and that fur- 

 nished by six or seven small creeks to be disposed of by evapora- 

 tion. But it is evident that the relation between supply nnd evaporation 

 is the reverse of what it is with Salt Lake ; for as the Jordan never 

 fails, (SO far as I am aware,) the supply must always be in excess of that 

 carried off' by evaporation. Its waters are well stocked with fish and 

 other aquatic forms of life. 



CLIMATE. 



As but very few meteorological records have hitherto been kept in 

 this basin, and these but for a few years only, and very irregularly, we 

 can only give an approximation to the means of temperature and raiu- 



* Air-lines aro to bo umlerstootl in ostimatini; thcso distances. 



