BAROMETRICAL AND METEOROLOGICAL ORSKKYATIONS. ITT) 



No. X was deduced from observations at Genoa. Carson Valley, Ctali, at an 

 elevation of 4,824 feet above the level of the sea, taken from June 12 to June 23, 

 1859. The mean temperature was 76°.o\ and the weather hue; but the condition of 

 the atmospheric pressure was not as uniformly regular as might have been desired. 

 The diagram has, therefore, a less marked shape and amplitude than onemight expect, 

 but it must be remembered that the situation of Genoa is » peculiar one. on the margin 

 of the arid interior, not far from extensive deserts, but also close to the foot of the 

 Sierra Nevada, with its snow-clad summits, its abundance of water, and luxuriant vege- 

 tation. 



I also tried to obtain the barometric variations in Woodruff Valley, one of the 

 desert valleys of the interior of the Basin, at an elevation of nearly 6,000 feet above 

 the level of the sea, at the end of May, 185!). The mean temperature there was then 53 : 

 Fahrenheit. But as a barometric storm occurred in these days. I did not obtain satisfac- 

 tory results. I can only state that the barometer seems to oscillate very little between 

 sunrise and noon, that then it sinks for some hours and begins to rise again rather 

 abruptly toward sunset. The peculiarity of this change is due to the influence of the 

 aqueous vapor, or rather to the extraordinarily small amount of aqueous vapor in that 

 region, as will appear from the discussion of that subject below, while we might expect 

 a large amplitude on account of the large daily oscillation of the temperature. 



These tables of oscillations were made use of for correcting the observations, either 

 directly or by combining them so as to answer the purpose more satisfactorily. Most 

 of the camping-places along our routes in- Utah did not require very large corrections, 

 partly on account of their high altitudes, which mostly varied between 5,500 and 

 7,000 feet above the level of the sea, partly on account of the reason stated above. 

 The largest corrections w ere needed in the neighborhood of Carson Lake, and at some 

 other low points with high temperatures; but in no instance were the oscillations found 

 nearly as large as those observed by Lieutenant Abbot at a much lower elevation with 

 higher temperature, in August, at Fort Reading, in the Sacramento Valley, or those 

 obtained farther south, in New Mexico* 



CORRECTION FOR 



THE ABNORMAL VARIATIONS OF THE ATMOSPHERIC PRESSURE. 



The amount of this variation differs much according to the elimatieal character and 

 elevation of the stations. There was no meteorological station in the interior of Utah, 

 in the elimatieal zone of our survey, besides that at Camp Floyd, where barometric 

 observations were taken under direction of the medical department of the Army. 

 Although we went several hundred miles from that place and passed high ranges of 

 mountains, 1 considered it safe to apply the corrections indicated by the changes of the 

 barometer at Camp Floyd, as it is a well-established fact that the variations extend over 

 hundreds of miles of the same zone with little change. Although we were part of the 



^^^ed^t^fi^i^yself merely to allude here to the change of the amplitudes, in vain, 

 th* different n, gradual or abropt increase or decrease of pressures 



?! r e S "nte t l in the diagrams ; nor can I discuss the varying ins:-. ' lie atmosphere 



a superficial examination. 



