( 4^7 ) 
^IV. Concerning the Magnet if m of Drilh i by 
Mr. Ballard. Communicated hy William 
Mulgrave, Feitow of the CoUedge of Fhyftci" 
ans and R. 
I. AS to the firfl: Pfopofition, viz, that a Drill in bo- 
JTx ring of Iron will acquire a vigorous Poiariry. I 
fuppQle it does not fully appear from hence, That all the 
common Drills in a Smith's Shop, which probably have 
been ufed moftly, if not only, in Iron, and never been 
within the Virtue or under the Touch of any Loadftofie^ 
do, with their Bitts, conftantly draw the South End of 
'the Needle 5 and confequently are themfelves a fixr N» 
Pole ; For I caufed Six or Seven feveral Drills to be 
made before my Face, and the Bitt or Point of every 
one became a N. Pole, only by hardening, before they 
ever came to be workt, either in Iron or any other mar» 
ter ; fo that I cannot fuppofe thofe found in a Shop to 
have gotten their Polarity fo much from their after uie^ 
as from their firft make. 
z. That pieces of plain Iron, in Shape like Drills, 
is (bmething long and fmall^ do always change 
their Poles as they are inverted, the end downwards 1^- 
ing ever the N. Pole ; I find not always true : For 
though it hold generally in fuchfmall pieces, and always 
(as far as I can yet find) in pieces of any Bulk, as large 
Hammers, Anvils, Andirons, Bars of Windows, ^c. 
yet I found feveral final! pieces of Steel, (uch as the Drills 
are made of, to have fixed Poles, one end North, the 
other South, in whatever Poftures I held them. Some 
of thefe very vigorous in fuch their Polarity ; others 
Slewing plainly a Tendency to fuch a Pole, rather than 
Q^qq th€ 
