C S°7 1 
much of the Virtue of the other ; by which means 
the hardeft End will have mod Power in directing 
the Card, and muft confequently make it vary to- 
wards its own Direction. If you retouch thefe 
Wires when fixed to the Card, the Error will ftill 
remain; for that Wire which is beft hardened will 
always become the ftrongeft. Confidcring how un- 
certain this Method of hardening the Ends of the 
Wires mud be, it is a great Chance if they fhould 
once in an hundred times be equally and uniformly 
hard : And unlefs they are, the Card to which they 
are fixed mud ncceflarily vary. 
The Wires being difpofed in the Form of a Lo- 
zenge, is the Reaion why thefe Cards had fo little 
Force, that they might be made toftand at theDiftance 
of feveral Degrees, on either Side the Point from 
whence they were drawn. For all magnetical Bodies 
receive an additional Strength, by being placed in 
the Direction of the Earth’s Magnetifm, and ad pro- 
portionably lefs vigoroufly when turned out of it. 
Wherefore, when thefe kind of Needles are drawn 
afide from their true Point, two of the parallel Sides 
of the Lozenge wi.l cotafpire more dircdly than be- 
fore with the Earth’s Magnetifm; and the other two 
will be lefs in that Direction : By which means the 
two firft Sides will very much impede its Return ; 
and the two latter will have that Impediment to 
overcome, as well as the Fridion, by their own 
Force alone. 
The Needles that arc ufed on board the Men of 
War, and fomc of the larger trading Ships, are 
made of one Piece of Steel, of a Spring Temper, 
and are broad towards the Ends, but tapering to- 
T t t wards 
