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A Memoir on the Magnetic Isoclinal and Isodynamic Lines 

 in the British Islands, from Observations by Professors 

 Humphrey. Lloyd and John Phillips, Robert fFere Fox, 

 Esq., Captain James Clark Ross, R.N., and Major Ed- 

 ward Sabine, R.A. By Major Edward Sabine, R.A., 

 F.R.S. 

 At the meeting of the British Association, held at Cambridge 

 in the year 1833, a resolution was passed, recommending that a 

 series of determinations of the magnetic dip and intensitj^ should 

 be executed in various parts of the United Kingdom. 



Early in 1834 Professor Lloyd, who had attended the meet- 

 ing at Cambridge, proposed to me to unite with him in carrying 

 the recommendation of the Association into effect as far as re- 

 garded Ireland. I was at that time employed on the staff of 

 the Army in the south-west district of Ireland, and found 

 it not incompatible with other duties to undertake that portion 

 of the island. Our observations were continued at intervals 

 throughout that year, and until the autumn of 1835, in the sum- 

 mer of which year we were joined by Captain James Clark Ross. 

 A report of our operations, drawn up by Professor Lloyd, was 

 made to the British Association, assembled in that year in Dub- 

 lin, and was printed in 1836 in the fourth volume of the Asso- 

 ciation Reports. A re-calculation of the Irisli results, incorpo- 

 rating the observations which have been made since in that part 

 of the United Kingdom, has been furnished by Mr. Lloyd, and 

 occupies its appropriate place in this i-eport. 



Mr. Robert Were Fox, who was present at the Dublin meet- 

 ing in 1835, brought with him an apparatus for magnetic ob- 

 servations on a new construction of his own invention, with 

 which, after the meeting, he made several observations of the 

 dip in the course of a tour in the west and north of Ireland. 

 These observations, with others made on his return through 

 Wales, were published in 1836, in the report of the Royal Po- 

 lytechnic Society of Cornwall for 1835. Several of these ob- 

 servations were made in houses, and were consequently liable 

 to disturbing influences. Mr. Fox has selected eight deter- 

 minations of the dip in Ireland, and nine in AVales, as free from 

 objection on this account; and with his permission they are 

 now incorporated in the present report. 



Having obtained two months leave of absence from military 

 duty in the summer of 1836, 1 employed them in extending the 

 survey to Scotland, by observations at twenty-seven stations dis- 

 VOL. VII. — 1838. E 



