190 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



because they are intercepted, in their forward and backward direction, by high ranges 

 of mountains. For the same reason the eastern winds are not very strong. The 

 northwest and north-northwest winds are still less numerous and weaker, because they 

 find still more obstructions. The average force of wind, including the calms, was 2.27, 

 and, including the hours of the night, by interpolation, probably 1.84. We may 

 account for this comparatively small force by the circumstance that the valley is 

 surrounded by high mountain ranges which break the force of the currents in the 

 lower strata of the atmosphere. Some very strong squalls were felt, however, lasting 

 for several hours. 



In No. IV D not the least corrections have been found necessary; but in No. IV 

 C some small corrections have been required, in consequence of the unsettled state of 

 the weather. 



No. V C and I) was deduced from 3 days' observations taken at Camp Floyd, 

 Utah, from August 6 to August 9, 1859. The mean temperature of these days was 

 69°.5 Fahrenheit; the mean force of vapor was 0.238 inch; the mean relative 

 humidity, 38.0, and the mean weight of vapor in 1 cubic foot of air, 2.59 grains troy. 

 No. V C and D correspond to No. V B, and very nearly to No. VI A, which may be 

 considered as forming together one set. No rain nor dew fell. The cloudiness of the 

 sky between the hours of 6 a. m. and 9 p. m. averaged only 0.56, but if we make 

 interpolations for the hours, probably to 0.62. The average force of the wind, includ- 

 ing the calms, between 6 a. m. and 9 p. m. was 1.7 ; fully one-half of the observations 

 showed northerly winds, with an average force of 2.5 ; 23 per cent, were calms, and 

 the remainder southerly and westerly winds. No. V C did not require the slightest 

 corrections, but for No. V D a few slight corrections appeared to be desirable, and 

 have been indicated. 



No. VI C and D was deduced from 3 days' hourly observations taken at Camp 

 Floyd, from September 15 to 18. The mean temperature was 64°. 7 Fahrenheit; 

 the mean force of vapor was 0.103 inch; the mean relative humidity was 21.9; the 

 mean weight of vapor in one cubic foot of air, 2.67 grains troy. Nos. VII C and 1) 

 correspond to No. VII B and No. X A, with which they form one set. The weather 

 was fine; no rain nor thunder-storms occurred. No dew was observed at camp, but 

 was formed most likely on the meadows below. The cloudiness of the sky between 

 the hours of 6 a. m. and 9 p. m. averaged 1.6; and including interpolations for the 

 night, probably 1 3. The clouds were mostly cumulo-cirri and some cumulo-stratus ; 

 over half of the time the sky was perfectly cloudless. The average force of the wind 

 between 6 a. m. and 9 p. m. was 1.6 including the calms, which lasted 18.5 per 

 cent, of the time; 23.8 per cent, were north and northeast winds, passing up the valley 

 with an average force of 1.7; 38.5 per cent, were south and southwest winds, blowing- 

 down the valley with an average force of 2.1; 11.3 per cent, were west and northwest 

 winds, passing down a narrow canon in the Sierra Nevada with a force of 2.4; only 

 7.9 per cent, were east winds, passing n ^ that canon with an average force of 1.1. 



The computed values of No. VII D appeared to require a slight correction at the 

 hours of 6 and 7 p. m., and- then No. VII C was changed slightly to make it corre- 

 spond better to D; but it is very likely that the uncorrected values are preferable, the 

 apparent irregularity being caused by the peculiar situation of the station. 



