 Compasses tended to " wander " from north when measurements were taken at different locations or even at a single location over a period of time . The astronomer Edmund Halley noted this and the problems it would cause for navigation in 1701 . It was also believed that whatever was causing this effect might be causing changes in the weather , and that studying magnetic variations might lead to better weather prediction . 
 Compasses tended to " wander " from north when measurements <a href='uninflect' title='1'><mark>were</mark></a> taken at different locations or even at a single location over a period of time . The astronomer Edmund Halley noted this and the problems it would cause for navigation in 1701 . It was also believed that whatever was causing this effect might be causing changes in the weather , and that studying magnetic variations might lead to better weather prediction . 
Compasses tended to " wander " from north when measurements was taken at different locations or even at a single location ova a period of time . The astronomer Edmund Halley noted dis and the problems it would cause fa navigation in 1701 . It was also believed dat whatever was causing this effect might b causing changes in the weather , and that studying magnetic variations might lead to betta weather prediction .