234  § Manufacture of Compass Needles. 
A remark or two as to the particular case which led to the 
use of these brass tips. If a scale of steel or iron was lodg 
in the plate, it is difficult to perceive how the simple shorten- 
ing of the needle would completely obviate the disturbance 
which it might occasion. It might render the error less man- 
ifest, but could not wholly correct it. 
As this subject is one of much consequence, particularly in 
this country, where the compass is so much employed, I will 
venture to add a few suggestions which, in my opinion, will 
be more likely to improve the manufacture of compass nee- 
dles, than the method proposed by Prof. Eaton. 
A person, upon purchasing a compass, if he wishes to ob- 
tain an accurate instrument, should test every part of the 
plate, limb, &c. with a fine magnetized sewing needle, sus- 
pended by a fibre of silk. If this is not at all affected by 
passing under it the different parts of the plate, it may be in- 
ferred that there is no point of attraction. But if it is af- 
ed, we can easily detect the exact spot in which the iron 
or steel is lodged. In the latter case, the better way is to se- 
lect another instrument and treat it in the same manner ; and 
ef 
inches in length and two in breadth,—Coulomb, and others, 
the arrow-shaped, &c. In one thing, however, most experi 
extremities consist of brass or silver? 
e effecte 
Finally, I imagine that it will be much easier to keep @ 
common needle properly pointed and free from rust, than it 
will be to obtain one of equal directive power, upon the plan - 
Proposed by Prof. Eaton. A SURVEYOR- 
a 
