j 
5 
BE 
S. Newcomb— Variability of the Earth's axial rotation. 163 
Mr. Glasenapp has just published his paper in the Russian 
language, the concluding part of which is devoted to this in- 
vestigation. He has also sent me the following more exten 
account of his investigation, from which I omit the citation of 
the original observations. 
_ “A great many preparations for the expedition of the transit 
of Venus, and the publishing of a Russian memoir on the 
observations of Jupiter's first satellite, have not allowed me 
take up the question of the variability of the earth’s axial 
rotation, which you proposed to me some time ago. But now I 
have investigated this very interesting question, and the result 
seems to me to be satisfactory, so that your hypothesis is very 
probable. 
“Tn the investigation I have chosen the two following ways: 
(1) I have tried if the corrections of noon: 
Year 1845 4+ 15 
1850 + 2 
1855 + 5 
1860 +10 
1862 +11 (1) 
1864 +10 
1866 + 6 
1868 2 
1870 0 | 
1872 — 2 
you sent to me in your letter dated October 24, 1873, ap- 
plied to the observed times of the eclipses of Jupiter's first 
satellite, will bring them in better agreement with the tables of 
Damoiseau than the uncorrected observations. The result I 
obtained is favorable, that is, the observations corrected by the 
Stites (1) are represented better than the uncorrected ones: 
thus your corrections seem to be rea ke ae 
“(2.) I determined the corrections of Damoiseau’s ecliptic 
tables of the first satellite for 44 different epochs (22 epochs from 
pe ae disappearing and 22 from eclipse reappearing), and it was 
sidered as constant quantities) change in the same manner as 
the corrections (1) you obtained from the observations of the 
“ Allow me to communicate to you the whole investigation 
of this interesting problem. 
1. First investigation. - ie 
“All the observations of the eclipses of the first satelite 
(as disappearing, as reappearing) from 1848 till 1873, which I 
