308 
MR, airy’s account OF THE HARTON EXPERIMENT 
Shields, and I explained the nature of the observations 
to an assembly of the residents of South Shields and its 
neighbourhood. 
1854. October 25. — The instruments were finally dismounted, and packed up for 
return to Greenwich ; and the party dispersed. 
24, In terminating this general history of the operation, it is proper perhaps that 
I should briefly allude to the sources from which the expenses were defrayed. 
The Royal Society, in granting the loan of their pendulums and clock, not only 
enabled me to undertake the operation with promptitude and with the security of 
using trustworthy instruments, but also removed one of the most serious causes of 
expense. I have already alluded to the extensive works constructed by the owners 
of the Harton Colliery, and which they made entirely at their own expense; and to 
the liberality of the Electric Telegraph Company, who gratuitously gave me their 
important assistance in the galvanic connexions. In transmitting the instruments 
from the wharfs at Newcastle to South Shields, Messrs. Stevenson and Co., of the 
Jarrow Chemical Works, gave the use of their river-craft. The Mayor and Corpo- 
ration of South Shields, unsolicited, caused the surveys to be made which were 
needed for computation of the attraction of the ground. Some parts of the appa- 
ratus (galvanometers, wires, stoves, &c.) were so evidently applicable to the pro- 
spective wants of the Royal Observatory, that they were not considered as a charge 
on the Experiment. The Lords Commissioners of the Admiralty, on my laying before 
them my proposals, contributed £100, which defrayed the greater part of the miscel- 
laneous expenses. The residual charges were borne by myself. 
Section II. — Comparisons of the Upper and Lower Clocks. 
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 15® 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, which were the corresponding obser- 
vations 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 
interrnjited 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 sliort delay, did the same. Then the observations were continued 
till the upper observer was satisfied with the number, after which he definitively 
