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THE MAGNETIC NEEDLE. 

 By A. W. Elkins, C.E., P.L.S., Lennoxville. 



(Read at the Autumn Meeting of the General Mining Association of the Province of 

 Quebec, at Sherbrooke, Que., September 2jth, i8g4.) 



A slender bar of steel, charged with some of that mysterious, 

 imponderable fluid or influence called magnetism, generally about five 

 inches long and about one sixteenth of an inch thich, pointed or wedge- 

 shaped at the ends, and provided at its centre with a cup-shaped piece 

 of very hard metal, or precious stone, so arranged that the bar may 

 freely turn upon a pivot, is essentially the simple little instrument known 

 to-day the world over as the Magnetic Needle, which possesses the 

 wonderful property of remaining in a direction, or of turning upon its 

 centre until it assumes a direction, nearly North and South, and this 

 provides data from which the direction of the geographic poles of the 

 earth can be inferred with a fair degree of accuracy. 



Such is the essential part of the instrument, which, for at least 

 seven centuries, has been the greatest boon to navigators, and of 

 inestimable service to explorers of unknown territory. 



The early history of this simple but invaluable contrivance is lost 

 in antiquity. It is thought that the Chinese were its inventors ; and one 

 authority states that the Emperor of Ho-Ang-Ti, marching with his 

 army against the enemy, finding himself embarrassed by fog, constructed 

 a chariot which indicated the South. This was in the year 2634 B.C., 

 and it is supposed that the Magnetic Needle was referred to ; but the 

 first time that it was explicitly mentioned was in a Chinese dictionary 

 finished A. D. 121. However, its use to navigators was probably not 

 generally known till the middle of the twelfth century. 



In order to bring forcibly before you some of the wonderful pro- 

 perties of the instrument, I will arrange a needle so that its extremities 

 will turn towards the poles. 



I have here a common knitting needle about seven inches long, to 

 which I have imparted some of that subtile, imponderable fluid or 

 influence, generally described as magnetism. 



Attached to the centre of this bar of steel is a fine silk thread b) 

 which I suspend the bar. 



!!2lLIBRAR 



