( 419 ) 
done the fidts, to deftroy and rub off, if I cou'd, all its 
former Polarity which was Southward; then offenng it 
again to the Needle, it drew the South end, and was 
quite changed. To confirm the thing, I toucht the 
lame Knife again witli the North Pole ot my Loadilone, 
and it drew vigoroufly the North End of the Needle. I 
whet it again ftrongly in the fame manner ,and it changed 
again. This I repeated five or fix times, and it ftiil 
changed by whetting, efpecially on the fides towards 
the top of the Knite, the very top and back, which 
cou'd not be whet to fo great an Heat, retaining ftili 
fome affedion for that Pole the Load ft one had enclin'd 
them to. This I try'd with a Knife of a thicker Blade ; 
but I could not with my Hand whet it to that Heat as 
to have the fame ESc&: wrought upon, as on m.y own; 
though I ufed fuch force as at laft to break it in two. 
I borrowed then another thinner ; but prefently had tfie 
fame Misfortune. 1 intend therefore to try it at a Cut- 
ler's Wheel, laid with Emery and Oyl ; and likewifeon 
a Grindftone, both wet and dry; and I rather choofe the 
Grindftone, becaufe the other Wheel may be fuppofed to 
have much Iron worn into it from the many Knives that 
have been ground on it, and fo the Effed if produced 
will prove no more than that of filing with, or drilling 
in Iron. And the wet Grindftone, though it wane 
Heat to give a new Polarity, yet probably ii nisy wear 
off thofe parts of the Iron in which the old did inhere, 
and fo render it fimple again. 
As to the 4th, Whether Brafs or Copper will, as well 
as Iron, give a N. Polarity to a Drill ; this cannot 
well be try'd; fince the very makifig, if it be well hard- 
ned, will certainly give it. Wherefore 
$. The Drill Mr. Hufit made could not, if well hard- 
en'd, according to what I can find, be indifferent to ei- 
ther Pole. 
Qj[q 2. 6.1 
