184 S. Newcomb on the apparent inequalities 
servations. Its cause was first discovered by La Place, who 
showed that it was due to the effect of the action of the planets 
in changing the eccentricity of the earth’s orbit. 
The results of his computations agreed substantially with ob- 
servations, and was therefore received with entire confidence until 
less than bialp hs years ago. The question being then taken up 
by Mr. John C. Adams, this eminent mathematician was led to 
the conclusion that La Place’s result was nearly twice too large. 
The same conclusion was reached independently by BS 
and gave rise to a remarkable discussion, the history of w 
is too familiar to be now recounted. It is now ee that 
the bent found by Adams and Delaunay is nai Hi correct. 
w result no longer agreeing with observation, the dif- 
ference te is now accounted for by an increase in the length of the 
day. That this length is increasing is also known from theoret- 
ical considerations, but the data for its accurate determination 
are wanting. 
dima ‘51 [or 15°39] sin (2 ND) +2) —3n0) 
Tf, in this ee ears: we substitute Hansen’s values of the 
elements, it becom 
Gi 5" i sin [173° 26’4-(1° 57-4) (#—1800)]. 
When in 1811 Burckhardt constructed his tables of the moon, 
e time and place when the discordance referred to was first distinctly attrib- 
set to the tidal retardation of the earth having been =* ae ter of dsensio, the 
following extract from an article on “‘ Modern Theore N 
American Review for October, — cl, ge P. vn may not be —— of interést. 
theory is the 
the conclusion, that rtion of the acceleration from some other cause 
than the attraction of gravitation, or the length of the creas- 
an extent W. e ptible from the cause to which we have 
already referred [the tidal ee p. 374]. as centuries roll by, the day 
shoul crease a move a little farther of a 
be p<, ace sould ce, in our calculations, we sup- 
posing an increase of some’ : 
Pere lenath ot the Gene anid al cictomponstiogs Ghadeainer the Gees ase 
