Galvano-magnetism. 143 
The author mentions the following facts in relation to increase of 
temperature in mines. : ye 
At Tingtang copper mine, in the parish of Gevennap, at the bot- 
tom of the shaft, at one hundred and seventy eight fathoms depth, 
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: their 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, 
about constructing a magnet, and having procured a bar of twen- 
'y 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. 
T then procured a beam capable of weighing six hundred pounds, the 
“am weighs twenty, and the armature ten; the whole was sustained. 
Tam 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. 
ay we not anticipate, that there will be some valuable application 
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 
