578 



Dr. G. E. Allan on 

 Table II. (June 15-22, 1906). 



Bar. 



Deflexion caused 



by remanent 



magnetism. 



Deflexion in 



reversed field 



of 40 C.G.S. 



Sgurr nan Gillean . . . 

 ! Storr 



Dim. 

 9-5 



mm. 

 160 



175 



8-5 

 26-5 

 15-0 



Dunvegan 



Stromness 



.Faule Ader 





On being tested about i two and a half years alter the date 

 on which the above observations were made, it was found 

 that all the bars had lost power, as shown in the next table. 



Table III. (Nov. 11-12, 1908). 



Deflexion caused 

 Bar. by remanent 

 magnetism. 



Deflexion in 



reversed field 



of 40 C.G.S. 



Sgurr nan Gillean . . . 

 Storr 



mm. 



87 



23 



mm. 

 12*2 



15-7 



8-1 



20-9 



11-6 



Dunvegan 



1-2 

 5-2 

 2-9 



Stromness 



Faule Ader i 







The loss of susceptibility amounts to from 45 to 61 per 

 cent, in the first four bars, and the increase of susceptibility 

 in the fifth bar brings it almost to an equality with that of 

 the first bar. 



Effect of Baking and Cooling. 



To test whether change of temperature alone could do 

 anything to restore or increase the magnetic quality of basalt, 

 the processes of baking in hydrogen and cooling in liquid air 

 were tried on two bars. 



