62 W. R. Grove, Esq., on the 



North- Western, and other companies. In the Ontonagon centre are 

 the Minnesota and fifteen other mines. 



At the Cliff mine three large steam engines are employed (1852) ; 

 with 250 men ; — and at the North American mine, two engines, 

 with 160 men. Most of the other mines, forty in number, are 

 assisted by steam-power. Three thousand miners are in work alto- 

 gether, and the general population is fast increasing. Native copper 

 is the principal object. Silver is always present, and occasionally in 

 masses of considerable size. According to authentic accounts, dated 

 February 1852, many new mines have been opened lately ; and all 

 are worked more systematically than heretofore, — generally by con- 

 tract. 



There are now in the Cliff mine masses of pure copper within view 

 estimated to weigh 700 tons in the whole ; and on the lands of the 

 Minnesota Company, one block weighing 250 tons. The copper 

 shipped in 1851 was about 1600 tons, valued at £130,000. This 

 copper is stated to be of great excellence in the manufacture of wire, 

 ordnance, and ship-sheathing. 



The large beds of specular and magnetic iron ore, on the south- 

 east side of the lake, are as yet only worked on a small scale. 



At this moment the business of mining has ceased on the Canadian 

 side of the lake. There is little doubt, however, but that profitable 

 deposits will, sooner or later, be discovered here. 



On the Heating Effects of Electricity and Magnetism.* 

 By W. R. Grove, Esq., M.A., F.R.S. 



In the early periods of philosophy, when any unusual phenomenon 

 attracted the attention of thinking men, it was frequently referred to 

 a preternatural or spiritual cause ; thus, with regard to the subject 

 about to be discussed, when the attraction of light substances by 

 rubbed amber was first observed, Thales referred it to a soul or 

 spiritual power possessed by the amber. 



Passing to the period antecedent to the time of more strict induc- 

 tive philosophy, viz., the period of the Alchemists, we find many 

 natural phenomena referred to spiritual causes. Paracelsus taught 

 that the Archaeus or stomach demon presided over, caused, and regu- 

 lated the functions of digestion, assimilation, &c. 



Van Helmont, who may be considered in many respects the turn- 

 ing point between alchemy and true chemistry, adopted with some 

 modification the Archaaus of Paracelsus and many of the opinions of 

 the Spiritualists, but shewed tendencies of a more correctly inductive 

 character ; the term ' Gas,' which he introduced, gives evidence of 



* Delivered in the Royal Institution, February 13, 1852. 



