THE EARTH A MAGNET. 15 



it a summer thunder-storm. "We were getting thoroughly 

 tired out, and the hcec olim meminisse juvabit with 

 which we had been comforting ourselves began to lose 

 its force. When at length we yielded, we learned that 

 we had gone many miles out of our road, and we did 

 not reach home till several hours after dark. Also the 

 offending compass was confiscated by justly indignant 

 parents, so that for a long while the cause of our 

 troubles was a mystery to us. In reality, instead of 

 pointing due north, the compass pointed more than 20 

 towards the west, or nearly to the quarter called by 

 sailors north-north-west. No wonder, therefore, that 

 we went astray when we followed a guide so un- 

 trustworthy. 



The peculiarity that the magnet needle does not, in 

 general, point to the north, is the first of a series of 

 peculiarities which I now propose briefly to describe. 

 The irregularity is called by sailors the needle's varia- 

 tion, but the term more commonly used by scientific 

 men is the declination of the needle. It was probably 

 discovered a long time ago, for 800 years before cm- 

 era the Chinese applied the magnet's directive force 

 to guide them in journeying over the great Asiatic 

 plains, and they must soon have detected so marked a 

 peculiarity. Instead of a ship's compass, they made 

 use of a magnetic car, on the front of which a floating 

 needle carried a small figure, whose outstretched arm 

 pointed southwards. We have no record, however, of 

 their discovery of the declination, and know only that 

 they were acquainted with it in the twelfth century. 



