742 Dr. Margaret Moir on Permanent Magnetism of 



cooling repeated. After that it was left for some three or 

 four months more, and tested again, but not this time sub- 

 jected to any further treatment. 



The most important results obtained for the six specimens 

 are collected and shown in tabular form below. 



Table I. 



<D 3. 



ap.l 



a S 

 9 £ 



12 



Cv bti 



« 5 



[ntrinsic 

 residual 

 lagnetism. 



6 

 a 



O 

 ft 



S) 



.£, 



'3 

 o 



g£ CO 



M S 



after heating 

 and cooling. 



Perct 

 lo 



P-t CO 



S~. 3 



,ntage 



9S 



be 



bp a 



*-§ 'o 



cS o 

 >* 3 





o 



- 



c 



O 



&i 



i— i 



X! O 



.O KS 



en g 



1 



660 



295 



28 



275 



245 



6-8 



9-5 



16-3 



4-05 



600 



374 



39 



354 



334 



53 



5-3 



10-6 



8 



580 



385 



46 



371 



364 



3-6 



1-9 



5-5 



12 



435 



332 



54 



328 



322 



1-2 



1-8 



30 



16 



340 



286 



56 



284 



278 



0-7 



2-1 



2-8 



20 



320 



252 



44 



239 



235 



52 



1-5 



6-7 



The specimens taken in order had to be given respectively 

 20, 30, 20, 12, 12, and 30 falls before further percussion 

 ceased to affect them, the first fall being generally the most 

 effective in reducing the magnetism. The first heating also 

 produced a greater reduction than any subsequent heating ; 

 and 7, 5, 4, 3, 3, and 4 successive heatings and coolings in 

 the case of the six specimens were sufficient to set up a cyclic 

 state, after which further heatings and coolings produced no 

 further change in magnetism. 



One peculiar point is, however, to be noticed in the be- 

 haviour of the first specimen. After having been heated and 

 cooled three times, when the magnetism at 100° 0. equalled 

 243 c.G.s. units and at room temperature 250 c.G.s. units — 

 that is, before the steady state had been reached, — the speci- 

 men was laid aside for about a month. On being examined 

 after that lapse of time, it was found that its magnetism had 

 in the interval spontaneously increased to 260 c.G.s. units. 

 Other two heatings, however, quickly wiped out this im- 

 provement, and when the temperature had been raised and 

 lowered yet other twice, a constant state was reached. No 

 indication of spontaneous improvement was noticed in any of 

 the other specimens examined, but in all the other cases the 

 alternate heating and cooling was continued until the steady 



