Capt. Scoresby’s Descriftkin of a Magnetwieter. 56l 
plate to such a depth, that their axis, or centre, precisely corre- 
sponds with the centre of the hinges ; hence the middle of the 
extremity of each bar is at the same elevation, and at the same 
distance from the needle in every position of the moveable limb. 
To give firmness to the instrument in making experiments, the 
table is fixed by the feet to a mass of lead, of seven or eight 
pounds weight. By means of this plate of lead, which has a 
screw at each corner, the whole apparatus is readily put into a 
horizontal position. 
With this apparatus, Mr Scoresby made a series of experi- 
ments, which are fully detailed in the Transactions of the Bdyal 
Society of Edinburgh, VoL IX., and of which the following are 
the principal results, 
1. Iron bars become magnetical by position, excepting when 
placed in the plane of the magnetic equator ; the upper end, as 
regards the position of the magnetic equator, becoming a south 
pole, and the lower extremity a north pole. ^ 
% No attraction or repulsion appears between a magnetized 
needle and iron-bars; the latter being free from permanent 
magnetism, whenever the iron is in the plane of the magnetic 
equator ; consequently by measuring the angle of no-attraction, 
in a bar placed north and south, we discover the magnetic dip, 
3. Before a magnet can attract iron, that is totally free from 
both permanent magnetism and that of position, it infuses into 
the iron a magnetism of contrary polarity to that of the attract- 
ing 
g pole. 
4). A bar of soft iron, held in any position, except in the plane 
of the magnetic equator, may be rendered magnetical by a blow 
with a hammer, or other hard substance ; in such cases, the 
magnetism of position seems to be fixed in it, so as to give it a 
permanent polarity. , 
5. An iron-bar, with permanent polarity, when placed any- 
where in the plane of the magnetic equator, may be deprived of 
its magnetism by a blow. 
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 
