334 Electro- Magfictic Experiments. 



The poles of ibis large magnet were altered, restored, or destroyed 

 with prodigous speed. It proved exceedingly well adapted to com- 

 municate a strong magnetism to bars of steel or compass needles. 



My next trial was, whether it would be possible to increase the 

 power of a common horse-shoe magnet of hardened steel. A mag- 

 net of this description, eight inches and a half high, weighing about 

 eight pounds, having lost much of its former strength, and capable 

 only of supporting about five pounds, was twisted round with brass 

 wire. It was exposed to galvanic action during several hours, but 

 its strength was not increased in the least degree. 



I am far from supposing that the utmost force which I was able to 

 produce by galvanism is the limit of what may be done, and I am 

 continually trying experiments, with a view of increasing the magnetic 

 force already produced. At all events, it appears that the produc- 

 tion by galvanism of a magnet capable of supporting one hundred and 

 fifty-four pounds, is a curious fact, which a few years ago could be 

 little anticipated. 



I took some pains to look over different books, in order to find ac- 

 counts of large magnets, either artificial or natural ; my trouble, how- 

 ever, was not well rewarded. I found but few and scanty accounts 

 of large magnets. 



An old Dutch traveller and painter, Andrees de Bruyer, speaks of 

 an immense natural loadstone, kept in the museum of Florence. 

 Lalande, in his Voyage en Italie, gives some further account of this 

 magnet ; but it is, as appears, unarmed, and therefore little can be 

 said of its real strength. 



One of the largest natural loadstones which I have seen is in the 

 museum of Teyler at Haarlem. It commonly supports one hundred 

 and fifty pounds weight ; but the connecting iron piece, the dish on 

 which the weight stands, &c. may be estimated at least at fifty pounds. 

 Thus the ordinary weight which this loadstone sustains is two hun- 

 dred pounds. But Mr. Van Marum asserts, that it is capable of car- 

 rying fifty pounds more, without dropping its load. The Teylerian 

 loadstone, therefore, the largest at least in this country, carries two 

 hundred and fifty pounds. 



Another loadstone in the same museum sustains fifteen kilogram- 

 mes or thirty pounds. 



A loadstone in the collection of the Society Felix Meritis at Am- 

 sterdam carries fifty pounds or twenty five kilogrammes. 



