66 HISTORY OF MAGNETISM. 



If we have seen reason to doubt the doctrine 

 of electric fluids as physical realities, we cannot 

 help pronouncing upon the magnetic fluids as 

 having still more insecure claims to a material 

 existence, even on the grounds just stated. But we 

 may add considerations still more decisive ; for at 

 a further stage of discovery, as we shall see, mag- 

 netic and electric action were found to be con- 

 nected in the closest manner, so as to lead to the 

 persuasion of their being different effects of one 

 common cause. After those discoveries, no philo- 

 sopher would dream of assuming electric fluids and 

 magnetic fluids as two distinct material agents. Yet 

 even now the nature of the dependence of mag- 

 netism upon any other cause is extremely difficult 

 to conceive. But till we have noticed some of the 

 discoveries to which we have alluded, we cannot 

 even speculate about that dependence. We now, 

 therefore, proceed to sketch the history of these 

 discoveries. 



