OF FEREOMAGNETIC WIRES BY MAGNETIZaTIOX. 3 



The accompanying figure shows the front and side views of the 

 apparatus. C is the magnetizing coil, and W the wire to be tested, 

 whose upper end is clamped to the support S, while its lower end 

 carries a weisrht O. M is a reflectino; mirror üxed to the rotatinjr 

 cylinder, the ends of which terminate in cones and fit lightly in the 

 agate cups on the heads of screws in brass sockets BB. K is a collimator, 

 L a lens,and E a micrometer with ocular scale. The slit of the collimator 



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III 

 Il I 



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 l|< 



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is illuminated by a gas flame ; the light leaves the collimator adjusted 

 for a parallel beam and is reflected by the mirror M and converges in 

 the micrometer field through the lens L. In the middle of the slit, a 

 very fine glass fibre is stretched parallel to the edge, the image of 

 which is clearly seen in the micrometer. A wire of about 1.5 mm. in 

 diameter touches the rotating cylinder under a suitable pressure ; if 

 the wire elono-ates or contracts, the mirror rotates throuo-h a small 

 angle and the corresponding displacement of the image of the fibre is 

 observed in the micrometer field. 



The masfnetizino; coil was 30 cm. lonof and o-ave a field of 37.97 

 C.G.S. units at the centre by passing a current of one ampere. The 

 current was measured by a Thomson graded galvanometer which 



