Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy

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                                Sect II. Comparisons of the Upper and Lower Clocks.

<s>27</s>25. In the ordinary state, the galvanic circuit was
interrupted at both circuit-breakers. At the pre-
arranged minute for commencing signals, as nearly
as possible, each of the observers completed the
connexion, and then gave his attention to the galvanometer.
The movement of the needle, at intervals of 15s nearly,
assured each observer that the other was prepared to
observe: and every observation of the clock-time of the
movement of the needle was then efficient for comparison
of the two clocks. Only, it was necessary to know precisely,
when the time of examining the written record of the time-signals should
arrive, <u>which</u> were the <u>corresponding</u> observations of the same galvanic
current. For this purpose, the following instructions were
given. After observing the clock-times of a few signals,
the upper observer interrupted the circuit during
one signal only, and then restored the connexion.
The lower observer, after waiting one or two minutes,
did the same thing. After another short delay, the
upper observer interrupted the circuit during two signals.
The lower observer, after a short delay, did the same.
                            
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Manuscript details

Author
George Biddell Airy
Reference
PT/54/5
Series
PT
Date
1855
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Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy, 1855. From The Royal Society, PT/54/5

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