4=26 Mr. W. Brown on the Effects of Percussion and 



Table V. (continued). 



Specimen III. 



Number of 

 magnet. 



Magnetic 

 moment, 

 per gram. 



Percentage loss due to 

 falling. 



Total loss. 



one time. 



three times. 



1 



2 



3 



4 



5 



63-86 

 71-55 

 68-89 

 71-55 

 71-25 



1-85 

 5-00 

 4-72 

 5-00 

 3-32 



0-94 

 1-09 

 5-40 

 1-74 

 2-14 



2-78 

 5-99 

 9-87 

 6-61 

 5-39 



Mean 



69-42 



3-98 



2-26 



6-13 



From this Table we see that the second annealing for two 

 hours has had no effect on the magnetic moment per gramme 

 in the case of specimens I. and II., and has only slightly in- 

 creased that of specimen III. We also see that the total 

 percentage loss is unaltered in I., and but slightly increased 

 in II., but in specimen III. there is an increase of about 

 33 per cent. 



All the magnets were now annealed for a period of thirty 

 minutes in an oil-bath at a temperature of 236° C; they were 

 then taken out and allowed to cool, as usual, to the ordinary 

 temperature of the room (8° C). Then, after lying aside 

 for six hours, they were magnetized in the same manner and 

 with the same battery-power as in the previous operations. 



The temperature of the oil was at first determined approxi- 

 mately by means of a mercury in glass thermometer ; it was, 

 however, accurately determined by an air-thermometer con- 

 structed on a method introduced by Mr. J. T. Bottomley, and 

 communicated by him to the Birmingham Meeting of the 

 British Association in 1886. This method will be explained 

 further on. 



After being magnetized, the magnets were laid aside for a 

 period of twenty hours and then put through another series 

 of observations, the results of which are given in the following 

 Table :— 



