FOR DETERMINING THE MEAN DENSITY OF THE EARTH. 
305 
thermometers, but with no other apparatus, w^ere to be interchanged, and a week’s 
observations were to be made in this state. The pendulums were to be interchanged 
a second time and a third time, so that, in the whole, four series of observations 
would be taken: but I thought it probable that less than a week would suffice for 
each of these latter series. 
22. On considering the amount of labour required for carrying out this plan, and 
considering also that it was not in my power to take an active part, I judged that six 
observers would be necessary. With the sanction of the Lords Commissioners of the 
Admiralty, I appointed Mr. Edwin Dunkin and Mr. William Ellis, Assistants of 
the Royal Observatory, as two of the observers. With the permission of M. J. John- 
son, Esq., I was enabled to solicit and to obtain the services of Mr. Norman Pogson, 
Assistant of the Oxford Observatory ; Professor Challis consented to my asking the 
aid of Mr. G. S. Criswick, Assistant of the Cambridge Observatory ; by permission 
of Professor Chevallier, Mr. George Rumker, Astronomer of the Durham Ob- 
servatory, joined the party ; and finally I w'as enabled, by the kindness of R. C. Car- 
rington, Esq., to avail myself of the services of Mr. G. H. Simmonds, Assistant of 
the Red Hill Observatory. Mr. Dunkin superintended the parly, and, during the 
observations, controlled the local operations of every kind. Under the admirable 
management of Mr. Dunkin, and the zealous and orderly assistance of all the gentlemen 
whom I have named, the work went on with the most perfect regularity, t cannot 
express how much I am indebted to the hearty cooperation of every individual 
Assistant during the whole course of the operations from the beginning to the end. 
Lodgings were provided for the party in the town of South Shields. Their com- 
fort, during their singular occupation, as well as my own on the occasions of my 
visits, were greatly increased by the uniform kindness of the authorities of the mine, 
and by the hospitable attentions of Robert Ingham, Esq., M.P., John Robinson, Esq., 
Mayor of South Sliields, James Mather, Esq., J. C. Stevenson, Esq., of the Jarrow 
Chemical Works, and other gentlemen resident in the town or neighbourhood. 
Attendants in the mine were selected and placed under the command of the observers 
by the owners of the mine. 
23. I may now give a brief journal of the operations. 
1854. August 5. — I examined the mine, and stations were selected. 
Instruments were procured, repaired, and sent to the Harton 
Mine; and observers were collected. 
September 26. — I went to South Shields. 
September 27. — I erected the clocks and pendulum at the upper station. 
September 28. — I erected the clocks and pendulum at the lower station. In 
the evening, four of the observers arrived. 
September 29. — In the morning, the remaining observers arrived. All were 
en)ployed in adjusting the pendulums, &c. and in the 
practice of observations. 
2 s 
mdccclvi. 
