254 DESCRIPTION OF A MAGNETIMETER, BEING A NEW 



6. Iron is rendered magnetical if scowered or filed, bent or 

 twisted, when in the position of the magnetic axis, or near this 

 position ; the upper end becoming a south pole, and the lower 

 end a north pole ; but the magnetism is destroyed by the same 

 means, if the bar be held in the plane of the magnetic equa- 

 tor, 



Exp. — Numerous experiments were made on the effect of these diffe- 

 rent kinds of treatment : the result, though varying a little as to 

 the intensity of the magnetism produced, was always the same as to 

 its quality. Any kind of shock, it seems, is sufficient to render iron 

 magnetic. A bar [No. 1.] dropped on its end from the height 

 of three feet on a carpet, became sensibly magnetic ; and dropped 

 on a stone received strong polarity, the lower end in each case be- 

 coming a north pole : the same bar then dropped horizontally on 

 the floor, in an east and west line, so as to strike the ground in the 

 plane of the magnetic equator, was immediately deprived of its po- 

 larity. 



7. Iron heated to redness, and quenched in water, in a ver- 

 tical position, becomes magnetic ; the upper end gaining south 

 polarity, and the lower end north. 



Exp. — Bar, No. 2. after being deprived of all magnetic virtue, was 

 heated red-hot, and quenched in water, in a vertical position. The 

 lower end was then found to repel the needle of the instrument, 

 when tKe moveable plate was in the plane of the magnetic equator, 

 8° ; the upper end attracted it about the same quantity. 



8. Hot iron receives more magnetism of position than the 

 same when cold. 



Exp. — The contrary of this has, I think, been generally assumed. 

 The experiments, however, were most decisive. An iron-bar, No. 2. 

 in a vertical position, at right angles to the north end of the needle, 



and 



