SCIENTIFIC MEMOIRS. 



VOL. v.— PART XVIII. 



Article IV. continued. 



Researches on the Electricity of Induction. By H. W. Dove. 



VI. Magnetism of the so-called unmagnetic metals, 



62. W HEN natural bodies are classified in relation to any phy- 

 sical agency, we soon find that the idea of antithesis by which the 

 substances may be distinguished in that respect from each other, 

 which at first presents itself, must be abandoned, for the action, 

 which in certain bodies is very energetic, and in others appears to 

 be entirely wanting, gradually diminishes throughout the series, 

 so that the transition from one to the other is imperceptible. 

 Thus between luminous and dark bodies phosphorescent sub- 

 stances intervene ; between conductors of electricity and insu- 

 lators, imperfect conductors ; diathermanous substances pass 

 gradually into athermanous, and conductors of heat into non- 

 conductors. But the transition of the magnetic metals to the 

 non-magnetic is so distinctly marked, that whilst all philosophers 

 are agreed respecting the magnetic properties of the former, the 

 possibility of magnetizing the latter has been as often maintained 

 as it has been denied. 



The process which, since the time of Brugmans, has always 

 been adopted to prove the magnetism of other substances 

 than iron and nickel, is, by endeavouring to direct and to move 

 readily mobile substances by means of powerful magnets, or, 

 vice versa, to direct and move easily mobile magnets by those 

 substances. The double magnetism of Hauy, and the fre- 

 quent use of astatic double needles since the invention of Le- 

 baillif's sideroscope, belong to the second method, whilst the 

 first has merely been modified by the different experimentalists 



VOL. V. PART XVIII. M 



