SABINE’S EXPERIMENTS. 45 
The clock, therefore, appears to have lost, on mean solar time, 32.632 
seconds per diem, between the 22d of December and the 3d of January, and 
to have made, consequently, 86367.368 vibrations in a mean solar day. The 
very near agrcement of the several particular results from whence the final 
deduction is derived, together with the number of days which comprise the 
interval, and by which, of course, any errors in the commencement and close 
(being the only errors which can affect the conclusion) are divided, justify a 
belief in the correctness of the determination. 
It would appear, also, that if this interval be divided into two portions, i. e. 
from the 22d of December to the 27th, and from the 27th to the 3d of January, 
the rate of the clock may be considered to have been the same in both por- 
tions, although this conclusion cannot be deemed so precise as the former, and 
may admit of a doubt, amounting to one tenth of a second in the twenty-four 
hours; it will be evident, however, that if the rate assigned to the one portion 
be in defect to that amount, it will be in a corresponding excess in the other, 
and that if the two portions of time be used as separate intervals, each for a 
distinct series of experiments with an invariable pendulum, the errors thus 
supposed in the assignment will mutually destroy each other in the mean 
of the results obtained by the two series ; and it will be further evident, that if 
a second invariable pendulum be employed in the second series, instead of the 
same in both, the rate of the one may be in defect, and of the other in excess; 
but their mean result will be the same as if the assignment had been pre- 
cisely correct ; or at least there will be no sensible difference. é 
The principal advantage of using two pendulums is to show, by the accord- 
ance of their result (within the limits of the above assignment,) that they 
have sustained no injury or alteration in the removal from station to station, 
but they also afford, incidentally, an evidence that the experiments at each 
station were sufficiently extended, when the result of each pendulum, sepa- 
rately, agrees, within the aforesaid limits, with their combined results. 
The pendulums which I employed were similar in all respects, except in a 
very trifling difference in length, equivalent, on an average of nine series of 
experiments with each, to nine seconds and seven tenths per diem; they 
were numbered 3 and 4, for distinction. 
4 
