BAROMETRICAL AND METEOROLOGICAL OUSKRVATIONS. 



the station of Camp Floyd, tiiey would correspond to an imaginary one a few 

 higher or lower. The altitude computed for Camp Eloyd would then he tl. 



this inmirinarv station, and the other altitudes would not be affected by that en 



all, but would he obtained correctly. Lastly. It might he douhted whether tin 



the elevation computed tor Camp Floyd might he incorrect. Frrors arising Iron 

 source would certainly he much greater if minor inland stations were directly 

 pared with the sea-level, than if they were computed with reference to a station 



and abnormal variations has done a -reat deal toward eliminating errors from that 

 source, but as these corrections cannot possibly be found to suit each single observa- 

 tion, I consider it the best policy to decrease the liability of errors in the results ot 



words, by assuming Camp Floyd as the lower station instead oi the level oi the sea. 

 The lowest portion of the route is lower than Camp Floyd, and I hesitated to 

 make use of that station as the fixed one. Still I considered it better to retain uni- 

 formity in the computations. The different values obtained for the altitude ot Genoa, 

 in Carson Valley, by the different modes of computation, will show the advantages ot 

 the method followed by me. Twelve days 1 careful observations had been taken there, 



the barometers at Genoa and Camp Floyd, as well as their mean readings for those 

 days, correspond well together, as I have stated above, and the temperature at the 

 time was very high at both points. If the altitude of Camp Floyd had been calcu- 

 lated from these observations only, by whatever method, it would have been found 

 very near equal to that of Genoa computed in the same way. By my method this 

 was obtained. I found Genoa 4,824 feet high, while Camp, Floyd is 4,860 feet high. 

 I then computed the altitude with reference to the mean reading at the level of the 

 sea, and the abnormal oscillation observed at Camp Floyd. I found it 5,004 feet, 

 which is much too high, because in this case, where the correctioHs give a nearly 

 exact compensation, the mean temperature of the year only would give a good result, 

 while the high temperature of these days, in connection with the great difference of 

 level between the upper and lower stations, raises the result unduly. Again, 1 com- 

 puted the altitude with reference to observations .luring the same days at San Fran- 

 middle of June at that place,' which, I felt satisfied, was larger than the correction 

 required for Genoa, but which might have been compensated by the high degree of 

 temperature. Thus I obtained the altitude, only 4,633 feet (as near as I could get it 

 without some corrections, the values of which were unknown to me). It will be seen 

 that the mean of these two extreme results. o.(h>4 ami 4.633, happens to be 4,818, very 

 near what my method gives. This example shows forcibly what I consider as the 

 advantage of computing from a fixed station, which does not differ too much in alti- 



