MAGNETIC SURVEY OF GREAT BRITAIN. J55 



Section II. — Scotland. 



§ 1 . Observations by the Statical Method.. 



Major Sabine s Observations. — These were made in the 

 summer of 1836, with the statical needle S (2) ; an account of 

 them is contained in the report on the Scotch Magnetical 

 Lines, in the 6tli vol. of the Reports of the British Association. 

 Between the 30th of July and the 4th of October, in which in- 

 terval the magnetism of the needle was shown to have sustained 

 no change, twenty-two stations were observed at, including two 

 in Ireland, viz. Bangor and Dublin. These are now transferred 

 to the Irish Series, and being thus included in their more appro- 

 priate place, will be omitted here. At the time of the publica- 

 tion of the Scotch report, no direct comparison had been made 

 of the intensity in Scotland with that in London ; but its values 

 at the several Scottish stations relatively to London were given 

 provisionally, by means of the observations in Dublin, and by 

 adopting 1'0208 as the ratio of the force in Dublin to unity in 

 London, according to a determination of Mr. Lloyd's, published 

 in the Transactions of the Royal Irish Academy, in 1836. The 

 values at the Scottish stations were consequently subject to 

 be altered by any modification which Mr. Lloyd's determina- 

 tion in Dublin might subsequently receive. In the present 

 report Mr. Lloyd lias given a corrected value for the force in 

 Dublin, resulting from a much larger number of determinations. 

 The corrected value is 1*0195. With this value, therefore, 

 and the comparative observations at Dublin and Helensburgh, 

 published in the Sjxth Report of the British Association, we 

 may now derive a more correct expression, relatively to London 

 for the intensity at Helensburgh as the base of the Scottish 

 determinations. 



The observations contained in the Scotch report presented 

 a double comparison between DubHn and Helensbui'gh : one 

 by the observations of the 22nd July, in Dublin, and the 27th 

 July, at Helensburgh ; the otlier by those of August 2, and 

 September 13 and 14, at Helensburgh, and October 4, at Dub- 

 lin. They are presented in the following tal)le. 



Note. — Between the first and second comparisons the needle 

 sustained an accident, which is related in the Scottish Report, 

 and which accounts for the angles of deflection being diflerent 

 in the two comparisons. 



