MAGNETIC SURVEY OF GREAT BRITAIN. 



163 



Omitting Tobermorie, for the reasons assigned in page 157, 

 and combining the results at the other twenty-one stations by 

 the method of least squares, we obtain the following values : 

 ar = + -000080; ?/ = --000118; u =-55° 46'; r = '000143. 

 The mean geographical position is latitude 56° o5', and longi- 

 tude 4° 15' W. 



Captain Ross's Observations. — These were made in the sum- 

 mer of 1838 with a cylinder (X) described in page 148. It was 

 vibrated at Westbourne Green, near London, in June and 

 July 1838, and again in December of the same year, having 

 been used in the interval both in Scotland and in Ireland. The 

 observations at Westbourne Green, showing that its magnet- 

 ism underwent no change in this interval, are contained in the 

 following table. 



Table LXIII. 



Table LXIV. contains the observations with cylinder (X) at 

 ten stations in Scotland, and at two stations in the north of 

 England, viz. Newcastle and Stonehouse. The values of the 

 total intensity in the final column, relatively to unity in London, 

 have been computed by means of the time of vibration of this 

 cylinder in London shown in the preceding table. 



