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Merchant-Ships had their Needles formed of two 
Pieces of (feel Wire; each of which was bent in the 
middle, fc as to make an obtufe Angle; and their 
Ends, being applied together, make an acute one; 
1 fo that the Whole reprefentsthe Form of a Lozenge; 
in the Centre of which, and of the Card, is placed 
the brafs Cap. I procured twenty Cards, with 
Needles of this kind fixed to them ; and after 
touching them with a Pair of large Bars, I tried 
each of them, with the fame Cup and Pin, by 
drawing them afidc 90 Degrees from the true Pointy 
and then feeing where they would reft. I found 
them all to vary more or left, either to the Eaft or 
Wed ; and fomc of them as far as 8 Degrees. Few. 
of them came to the fame Degree twice together; 
and when they did, that was never the true Poiur. 
In fliort, they not only varied from the true Direc- 
tion, but from one another, and from themfclvesy 
I then tried, by drawing tlum gently allde, how far 
I could make them ftand from the true Point, with- 
out returning; and found they might frequently be 
made to do it at the Diftancc of a whole Point on 
either Side. One of them, which generally varied 
6 or 7 Degrees to the Eaft, being drawn the lame 
Way, would ftand at 16 Degrees. 
. All thefe Irregularities arc owing to the Stru&ure 
of the Needle : For the Wires, of which it is com- 
pofed, are only hardened at the Ends ; and that is done 
by making the Ends red hot, and quenching them 
in Water : If all thefe Ends are not equally hard, or 
if one End be hardened higher up than the other, 
when they come to be put together, in fixing them 
to the Card, that End which is hardeft, will deftroy 
- - much 
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