36 ’ SABINE’S EXPERIMENTS. 
- known, with as rigorous an exactness as if the measurements had been made 
at both places by the original procedure: this mode is founded on, a well 
known property in pendulums, that their lengths are inversely as ‘the squares 
of the numbers of their respective vibrations in equal times: the process 
‘consists in determining, accordingly, the number of vibrations of an inva- 
riable pendulum of comparison at the two stations; i. e. where the length 
is already known, and where it is purposed to be known. 
It is this latter method which | have employed to ascertain the difference 
in the length of the seconds pendulum in London, and in New York; and, 
by consequence, the absolute length at the latter station, on the presumption 
that it has been correctly determined at the former. 
The possible value, then, of the experiments which form the subject of 
this paper, beyond their immediate object of assisting in the determination 
of the figure of the earth, may be thus stated: should it be desired to esta- 
blish a standard in nature within the territory of the United States, where- 
with to compare and perpetuate the ational scale of linear measure; and 
should New-York be deemed in other respects an unexceptionable locality 
at which to institute a series of experiments for this purpose, or either of the 
original methods of London or of Paris, an oppprtunity is hereby presented 
of comparing the result of such an operation with that which has been ob- 
tained in London, and which is now conveyed to New-York. by pendulums 
of intermediate comparison. ; 
I proceed to the detail of the observations, which it is purposed to give 
at sufficient length to enable each individual to judge for himself of the de- 
gree of accuracy to which the conclusions may be considered to be entitled. 
The experiments were made in Columbia College, by permission of the 
President and Trustees of that Institution, most kindly tendered as soon 
as my intention was made known to them by Dr. Hosack, and as thank- 
fully accepted, since it is important that determinations of this nature should 
be made in public edifices, rather than in the houses of private individuals, 
as affording a greater probability of convenient access on future occasions 
of similar or connected operations. A vacant apartment, opposite the door 
leading into the gallery of the Chapel, was assigned for the pendulums, and 
the use of the Cupola permitted as a temporary observatory. 
So 
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