118 
CHRISTIE. 
graph station is still running, and another section can be 
very soon added there. The Governors Island, Sandy Hook, 
and Fort Hamilton series can be treated as a single series 
nearly half a century long, and doubtless many more will 
be reduced both in this and in foreign countries. Since the 
non-rigidity of the earth is not known, the divergence of 
the axes of rotation and figure have been computed, on the 
supposition that the earth is rigid, for comparison with the 
results from astronomical observations. In this way we 
may come to have a measure of the non-rigidity. 
Recapitulation. 
Revised Results at San Francisco , California. 
Mean position of stations {longitude! 122“ 28''.4. 
427-day distri¬ 
bution. 
440-day distri¬ 
bution. 
456-day distri¬ 
bution. 
Date. 
Aug. 18, 1873 
July 25, 1872 
Dec. 22, 1871 
d. d. 
d. d. 
d. d. 
Period. 
437.6 dr 2.3 
437.0 dr 1.0 
437.7 dr 2.0 
ft- ft- 
ft. ft. 
ft. ft. 
«i . 
0.051 dr 0.007 
0.056 dr 0.007 
0.063 dr 0.008 
h . 
207° dr 15° 
173° db 7° 
349° dr 14° 
reduced to mean date.. 
120° d- 15° 
125° dr 7° 
124° dr 14° 
Giving these three distributions of substantially the same 
data equal weights, and taking for the probable error of the 
mean simply the mean of the probable errors, as not too 
great, we obtain 
Civil date = September 21, 1872. 
Julian date = 2405058 
Period = 437?4 ± L8 
ft. in. mm. 
a x = 0.057 = 0.68 = 17.4 = 0".17 
zb 7 zb 8 zb 2.1 zb 2 
e 1 = 123° zb 12° , 
