186 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



be very slow, and therefore inaccurate at times when the temperatures changed rapidly ; 

 besides, the instrument proved inconvenient for use in the field, and was badly con- 

 structed, the two thermometers not reading conformably, and thus making corrections 

 necessary in the records. 



The following tables, C and D, exhibit the mean daily oscillation of the elastic 

 force of vapor, and of the relative humidity of the air, at certain stations and seasons, 

 as deduced from our observations. They are graphically represented in the plates, C 

 and D. The full black lines of the diagrams connect the values obtained for each suc- 

 cessive hour by direct calculation. Where dotted lines run alongside of the full lines 

 they illustrate the actual result of calculation, inclusive of all irregularities, while then 

 the full lines represent the values which I am led to consider as the means unimpaired 

 by the abnormal oscillations produced by irregular rains, high winds, and similar cas- 

 ualties. In the tables C and D, the values are given only for the hours during which 

 observations have been taken.. In other subsequent tables I have given the values 

 obtained for the hours of the night, by interpolation, which are also graphically repre- 

 sented on the diagrams by dotted lines. They were obtained by drawing, in the dia- 

 grams of the oscillations of temperature, of the force of vapor, and of the relative 

 humidity, separately and independently of each other, the curves for the hours of the 

 night, such as they appeared to be, required under the circumstances. Then I calcu- 

 lated from two of the thus-obtained values the third, and represented it also on the dia- 

 grams. If the discrepancy between the first and second values was beyond the limits 

 of the differences found to exist between the means of the computations of the single 

 observations and the values computed from the means of these observations at the 

 actually observed hours, then I critically examined the diagrams and changed them 

 accordingly, until all the requirements appeared to be fulfilled. I am confident that 

 they will be found to agree very closely with the results of observations which in future 

 may be made in this line. In computing, I have made use of the meteorological and 

 physical tables prepared for the Smithsonian Institution by Prof. A. Guyot, second edi- 

 tion, particularly of Tables B, VI, VII, IX, and X, which are deduced from Regnault's 

 formula and the values obtained by him in his famous investigations on the vapor, 

 instituted by order of the French government. In many instancesT could not make 

 use of the tables directly, because they do not extend to the quite abnormal extremes 

 which my observations exhibit. 1 then had to apply directly the formula. The results 

 of all the single computations will be found in the records of meteorological observations 

 accompanying the report. The means in the following tables, C and D, were calcu- 

 lated without making the slightest discretionary corrections in the single observations, 

 because I consider it impossible correctly to estimate the abnormal influences exercised 

 upon the values by irregular changes of wind and weather, and that it is best to leave 

 them to be balanced against each other. 



