PRESIDENTIAL ADDRESS, S.T.E., 1874. 217 



the earth acts as a great magnet how it is a 

 magnet, whether an electro-magnet in virtue of 

 currents circulating round under the upper surface, 

 or whether it is a magnet like a mass of steel or 

 loadstone, we do not know. 



When the phenomena of terrestrial magnetism 

 were first somewhat accurately observed about 300 

 years ago, the needle pointed here in England a 

 little to the east of north ; a few years later it 

 pointed due north'; then, until about the year 1820, 

 it went to the west of north ; and now it is coming 

 back towards the north. The dip has experienced 

 corresponding variations. The dip was first dis- 

 covered by the instrument-maker Robert Nor- 

 man : an illustration, I may mention in passing, 

 of the benefits which abstract science derives from 

 practical applications one of the most important 

 fundamental discoveries of magnetism brought 

 back to theory by the instrument-maker who made 

 mariners' compasses. Robert Norman, in balanc- 

 ing his compass-cards, noticed that after they were 

 magnetized one end dipped, and he examined the 

 phenomenon and supported a needle about the 



