EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



South wind 



South-southeast wind . 



Southeast wind 



East-southeast wind. . 



East wind 



East-northeast wind . . 



2.1 



1.7 



Northeast wind 



North-northeast wind . 



North wind 



Southwest wind 



South-southwest wind 

 Calmness 



11.1 



0.0 



From north-northwest and west-southwest no wind occurred during this time. 

 The average force of the wind, including the calms, was 3.65, exclusive of the night. 

 The only slight discretionary correction of the obtained mean values was made in C 

 at 5 p. in. and 6 p. m., as indicated in the diagram, where an evident irregularity 

 occurred, probably caused by some abnormal change in the atmosphere, rain-storm, 

 or the like. 



No. II and D was deduced from 4 days' observations taken at Fort Laramie, 

 Nebr., from July 30 to August 3, 1858, at an elevation of about 4,470 feet above the 

 level of the sea. The mean temperature of these days was 67°.0 Fahrenheit; the mean 

 force of vapor was 0.344; the relative humidity, 57.0; the mean weight of vapor in 1 

 cubic foot of air, 3.78 grains troy. Nos. II C and D correspond to No. II B and No. 

 II A; they form altogether one set. It had thundered, and rained a few drops, shortly 

 before the first observation was taken, and it rained twice afterward, for.a few moments; 

 but the average quantity of rain was scarcely 0.01 inch. Dew was observed every 

 morning near the river. On 2 of the evenings sheet-lightning was observed, and once 

 distant thunder. Thunder-storms are numerous in that neighborhood and season. The 

 cloudiness of the sky between the hours of 6 a. m. and 9 p. m. averaged 4.62, and, 

 including interpolations for the night, 4.37, the clouds being mostly cumuli. This 

 increased cloudiness compared with Fort Kearney, while the relative humidity is, on 

 the contrary, less, is a consequence of the neighborhood of the highly-elevated sum- 

 mits of the Rocky Mountains, the lower temperature and comparative moistness of 

 which favors the formation of clouds, which, however, dissolve again when they sink 

 into the lower regions of the air. Of the 64 observations of the wind during these 4 

 days, between 6 a, m. and 9 p. m. — 



24 showed easterly winds, including N. E. and S. E., with average force of 2.4. 



14 showed westerly winds, including N. W. and S. W., with average force of 3.0. 



13 showed northerly winds, including N. N. W. and N. N. E., with average force of 2.0. 



3 showed southerly winds, including S. S. E. and S. S. W., with average force of 2.0. 



10 showed perfect calmness. 



The average force of wind, including the calms, was 2.0. The wind shifted con- 

 tinually, and this, in connection with the peculiar situation of Fort Laramie, at the 

 foot of the high range of the Rocky Mountains, and bordering on the vast arid plains, 

 in consequence of wdiich the shifting wind at once brings currents of air of a quite 

 different temperature and degree of- moisture, makes the observed values of No. II C 

 and D somewhat irregular, which irregularity is increased by the influence of the two 

 thunder-storms. Some discretionary corrections have, therefore, been required. 



