34 [June, 1841. 



To observe the time and degree of rapidity of resuming the mag- 

 netic power by a mass of melted iron, a bed was formed about 3 or 

 3 1-2 feet in length, 5 inches deep, and of the usual form for cast- 

 ing pig iron ; rounding at the bottom and 4 or 5 inches broad at 

 the top. The length of this bed was nearly in the direction of the 

 magnetic meridian. 



A compass needle 3 inches long was placed near the northern 

 end of the bed, but a little to the east, and about 5 inches short of 

 the extremity ; another needle about 7-8 of an inch long, was placed 

 symetrically to the west side of the bed, and about the same dis- 

 tance from its southern extremity. Thus a line joining the centres 

 of the needles, would pass over the centre of the pig bed, and be 

 about nine or ten inches shorter than the latter. 



The needles having come to rest, and their positions been noted, 

 the bed was filled with melted iron. A slight derangement of the 

 needles occurred while the ladle was near, during the pouring of 

 the metal ; but they soon recovered their previous position, as 

 soon as the ladle had been removed. 



They were then carefully watched in order to detect the first 

 movements which should occur after the solidifying of the pig. 



At the end of 20 minutes the metal being cooled down to a heat 

 which made it barely red in daylight, the first movements were 

 detected, slow and scarcely perceptible, but increasing in rapidity so 

 that at the end of two minutes, the divergency amounted to 8 ; in 

 4 minutes it had extended to 20, the pig being nearly black ; and 

 in 20 minutes more, the divergency had attained its maximum of 

 22 from the original position. As the influence of the earth's 

 magnetism converted the northerly part of the pig into a north 

 pole, it of course repelled the north pole of the needle placed near 

 it, and attracted the south. The reverse taking place at the oppo- 

 site end of the pig, the north end was there attracted and the south 

 repelled. To ascertain whether any degree of permanent magnetic 

 force would be retained by the pig, it was thrown from its bed and 

 caused to make one-fourth of a revolution horizontally, so as to 

 bring its longest diameter into the magnetic east and west. In 

 this, position it exerted no power on the needle brought near either 



