320 CALIFORNIA ACADEMY OF SCIENCES. 



the computing division of the Survey, under the direction 

 of Assistant Schott. From the means abeady at hand, the 

 following summary of results is made known, wherein it is 

 seen that the accej^ted standard station for latitude is Mount 

 Helena, and the standard line for azimuth is Mount 

 Helena — Mount Diablo. The tabulation exhibits the ob- 

 served and computed latitudes and azimuths, the probable 

 error of each determination, and the deflection of the plumb- 

 line from the means. 



Including the stations Mount Lola and Kound Top, 

 which are the eMsternmost points of the " Davidson Quadri- 

 laterals," in the Sierra Nevada, we have nine stations, at 

 each of which the latitude and azimuth were determined as- 

 tronomically; and we shall take the mean results derived 

 from all these observations for the formation of the stand- 

 ard values cTq and «o. 



The direct results of the astronomical observations for 

 latitude require two corrections: one, the reduction to the 

 station point A; the other, the correction for curvature of 

 the vertical or reduction to the sea level. The heights re- 

 quired for the latter purpose are given in Appendix No. 10, 

 Coast and Geodetic Survey Eeport for 1884, (Mount Lola 

 being 2,796.4 metres, or 9,175 feet; and Bound Top 3,173.5 

 metres, or 10,412 feet above the level of the sea.) 



For the expression of the curvature between the sea-lev- 

 el and the altitude of the station, we have (see Clarke's 



Geodesy, pp. 101-102), d <p= !^7-, (| m—e) sin 2<p. Put- 



r sm X 



ting I m— e'=0.0052 \ and log. (r sin r0=1.490,then for A, 



the height in metres, and 'V the correction in seconds of 



arc we have for the latitude <p 



0^=— 0.000167Asin2^; or [7i6.212]A, 



for the average latitude 39°; the number within brackets 



being a logarithm. 



^ — G. Zaebariae. in his Principal Geodetic Points (German transla- 

 tion by Dr. Lampe, Berlin, 1878), prefers the value 0.00513. 



