MAGNETIC SURVEY OF GREAT BRITAIN. 



195 



In order to render the view in this Map of the magnetic 

 phenomena in the British Islands more complete, I have added 

 the direction, shown by arrows, of the horizontal or compass 

 needle at three extreme stations, determined by Captain James 

 Clark Ross, viz. Lerwick, in the Shetland Islands ; Valencia, 

 at the S.W. extremity of Ireland ; and Bushey, near London. 

 The geographical positions of these stations, and the variations 

 observed at them, are as follows, the latter being the mean va- 

 riation at the epoch named, obtained by observations repeated 

 every fifteen minutes from 7 a.m. to 7 p.m. for several succes- 

 sive days. 



