MAGNETIC SURVEY OF GREAT BRITAIN. 



161 



Collecting the results in one view, we have as follows 



Table LXI. 



If we combine the results at these nine stations by the 

 method of least squares, we obtain the following values : 

 x=+ -000080 ; 2/ = - '000069 ; m = - 40° 38' ; r = -000106. 

 The mean geographical position is in latitude 56° 52' and lon- 

 gitude 2° 45' W. 



§ 2. By the Method of Vibrations. 



Major Sabine's Observations. — These observations were 

 made in the summer of 1836; a detailed account of them is 

 given in the Sixth Report of the British Association. Two 

 cylinders, L a and L b, were vibrated at twenty-two stations in 

 Scotland, between the 28th July and 18th September, during 

 which interval the magnetism of the cylinders was proved to 

 have been steady. The times of vibration at the several stations, 

 reduced to a temperature of 60°, are inserted in Table LXII., 

 being taken from the Sixth Report of the Association. The 

 values of the horizontal intensity are given in the table in re- 

 lation to unity at Helensburgh ; and those of the total force to 

 unity in London : the intensity at Helensburgh having been 

 already shown to be as 1 -0258 to 1 '0000 in London. 



