Galvano-magnetisni. 143 



The author mentions the following facts in relation to increase of 

 temperature in mines. 



At Tingtang copper mine, in the parish of Gevennap, at the bot- 

 tom of the shaft, at one hundred and seventy eight fathoms depths 

 the water was at the temperature of 82'^. In 1820, when the same 

 shaft was one hundred and five fathoms, the temperature was 68° ; 

 thus an increase of 14° has been observed in sinking seventy three 

 fathoms. 



At Huel Vor, the water was 69°, at one hundred and thirty nine 

 fathoms, in 1819. It is now two hundred and nine fathoms deep, 

 and the temperature is 79°. 



At the bottom of Poldice copper mine, in 1820, at one hundred 

 and forty four fathoms, it was 80°. Now, at one hundred and sev- 

 enty six fathoms, it is 99°, and in a cross level, twenty fathoms far- 

 ther north, the water is 100°. The two last are the highest tem- 

 peratures observed in any of the mines of Cornwall. The water 

 pumped up from this part of the mine was estimated at one million 

 and eight hundred thousand gallons in twenty four hours. 



Art. XVIII. — Galvano-magnetism. 



The communication of Prof. Henry, in our last No., induced Prof. 

 J. W. Webster of Harvard University, and Dr. Hare of the University 

 of Pennsylvania, to repeat the experiments : theii* statements are 

 annexed. 



Dr. W. in a letter to the editor, dated Feb. 7th, 1831, says— - 

 immediately on receiving the last No. of the American Journal, I 

 set about constructing a magnet, and having procured a bar of twen- 

 ty inches in length by two, arranged it in a frame. With five hun- 

 dred feet of fine copper wire, and a single coil of copper and zinc,- 

 of three inches by two, it sustained all the weights I had at command. 

 I then procured a beam capable of weighing six hundred pounds, the 

 beam weighs tv/enty, and the armature ten ; the whole was sustained. 

 I am to lecture next week to the Mechanics' Institution in Boston, 

 and shall use it in this state ; after which, I intend to proceed to 

 the maximum. I have no doubt it will carry twelve hundred pounds. 

 May we not anticipate, that there will be some valuable application 

 of this power in the mechanic arts ? Every thing being adjusted, we 

 have only to lift a tumbler of acid and water to the coil, and the 



