i;ai;omktkical and METi-:oitOLOiiiCA 



•tively; while at Philadelphia it was sm 



tal .to September, viz, 82.f>, with amplitude, 



decreased, tin 

 valley of Can 

 perhaps carri, 

 mometer betv 

 marked by a i 

 due to the pt 



cause the loftiest summits of 



the Sierra in the nci 



ghborhood we 



re still covered wi 



snow, the whole lower portic 





many miles in 





been overflowed, and the e* 



ensive sheet of water i 



[>f hake lh.der 



commences not me 



than 2 or 3 miles from Gem 



►a. It indicates that 



Carson Vallev 



decidedly belongs 



the climatical svstem of the 



vast deserts of Cars< 



m Lake, of tl 



ie sink of Bumbol 



River, &c, and that its pecul 



liar climatical feature* 



, are chiefly de 



rived from them. 



The curve Xo. I of For 



t Kearney, also, for J 



'une, is much i 



nore similar to that 



Philadelphia, The maximu 



in is 89.6, the minin 



mm 68.4* whi 



le at Philadelphia t 



maximum is 1)3, the minium 



mi 64, at 3 and 4 p. i 



n., the amplitu 



de therefore 29, wh 



the mean is ISA). We tin 



is find, again, that tl: 



ie neighborly 



)d of Fort Kearm 



although arid compared witL 



i that of the eastern c 



oast, and mud 



i less adapted to ag 



cultural pursuits, is still moi; 



st compared with that 



of the desert 



valleys of Utah. 



The diagram Xo. Ill, o 



btained at Fort Bridg 



er in the first i 



lays of September. 



also very remarkable. The 



maximum, just before 



sunrise, about 



3 a. m., was 40. r l 



saturation then declined rapi 



dly with the increas 



ing temperatur 



e, and was nearly s 



tionarv between a. m. and 



2 p. m., about 10; th 



en it began to 



increase uniformly 



the weather at the time. Fort Bridger is situated in a low meadow, well watered by 

 several branches of a creek. Strong western winds prevailed at the time, which, com- 

 ing from the arid regions of the Great Basin, were extremely dry. Under their influ- 

 ence the saturation decreased verv rapidly with the increase of the temperature. Bv 

 9 o'clock, however, the temperature had become sufficiently high to produce a powerful 

 evaporation on the moist surface which balanced the desiccating influence of the wind. 

 With the declining temperature, after 3 p. m., the evaporation becomes also less, and 

 the dry western winds exercised a greater influence upon the saturation of the air than 

 the declining temperature. The relative humidity could, therefore, only increase very 

 gradually and slowly during the night. 



I may remark that the difference between the mean values of the relative humidity 

 obtained from the computation of the single observations, in several instances, differs 



