SABINE’S EXPERIMENTS. B37 
A common, though very good astronomical clock, was firmly attached to 
the wall of the apartment, nearly opposite the door; a strong iron frame 
designed to support a detached pendulum, the rate of which on that of the 
clock it was proposed to ascertain, was fixed at a proper distance above the 
clock, by screws of five inches in length, working in pickets of wood dri- 
ven into the wall; the iron frame, the pendulum, and its agate support, 
corresponded in all respects to those used on a similar occasion in Great 
Britain, and described by Captain Kater, in the Philosophical transactions for 
1819, pages 341, 342; and I may here remark, that the method of deter- 
mining the number of vibrations in 24 hours of the invariable pendulum, 
by the interval elapsing between its coincidences with that of the clock, is 
the-same as is described. in an earlier paper of the same writer, in the vo- 
lume for 1818, page 43, with this exception, that 1 am in the habit of noting 
the time of re-appearance of the disk on the pendulum of the clock, after 
its coincidence with the detached pendulum, as well as the time of its dis- 
appearance previous to the coincidence ; and that the second which is com- 
pleted after they have been seen to pass the opening in the diaphragm of the 
Telescope in apparent coincidence, and the one which is completed before 
the first appearance of their separation, are registered as the respective 
times, and their mean is considered as the true time of coincidence. 
By favour of the gentlemen who superintend the administration of the 
customs in New-York, the instruments had been permitted to be landed not 
merely without duty, but without undergoing the customary formality of in- 
spection, in consideration of the public utility of their purpose: they were: 
disembarked on the 11th of December, being the day after my arrival, and 
were ready to have commenced the observations on the morning of the 15th ; 
the weather, however, proved an obstruction until the 22d; a delay which 
may have been ultimately beneficial, in giving time to the astronomical clock © 
to take up a more steady rate than it might possibly have had in the ear- 
lier days. . ) 
The pendulum being invariable in all respects, excepting in the effects of 
heat, an exact knowledge of its temperature at the times when its vibrations 
are under notice is essential to accuracy. In the attainment: of this know- 
