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16 Improvement in manufacturing Magnetic Needles. 
ticular point. On consulting Mr. Hanks, he said this might 
frequently happen, and it was not improbable that all those 
fits complained of by surveyors, might be traced to the same 
cause ; inasmuch as all compass cards and graduated circles 
were wrought with very fine steel instruments. To illustrate 
the subject, I took out the screws from the under side of the 
card and inserted the point of the Snes te) se eed le, less 
than the twentieth of an inch in length ;_ y I actually 
produced four additional points of disturbance. 
To obviate the difficulty, Mr. Hanks cut off seven tenths of 
an inch from each pole of the needle, ground the poles to 
very sharp points, and tipped them with brass caps, extend- 
ing to the original length of the needle. This measure, by 
Sestceaneing. the magnetic poles from the sphere of attraction, 
oved a perfect remedy. Mr. Hanks presented the same 
Pormpass to the school, where it has been almost daily 
for two months ; | it is one of the most instruments 
that I have - used. It has no more fits, andi is folay un- 
disturbed b aaanetic ores, real or imaginary. anks 
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has since corrected a theodolite in the same way, w hich had 
been thrown aside as useless for several years. If the dis- 
turbing steel scale is in the card near the graduated aoe 
Mr. H. proposes lengthening the pivot and raising the cir 
by intreducing an additional atoe beneath the raiinted 
ene. But he has not made this experiment ; and ti ds proba- 
ble no such case willever occur. For if it were near the pivot, 
it would not disturb the needle; and so little work is required 
in the card with slender i instruments, that scales will not often 
be left in that part 
Another i important advantage which will attend tipping 
needles a given brass, Xc. is that of preserving the points 
from ru has’b been demonstrated by conclusive. experi- 
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ments, aa ee resembles electricity in acting most 
powerfully from t ‘sharpest points. Hence the absurdity of 
are bars. Hence, also, the utility of pre- 
serving the finely sharpened points by tips. _ I will add, that, 
of all sor of needles which I have used, the flat kinds are 
ich are wide in the middle, and of a true taper to the 
Vouvs respectfully, 
Amos EATon. 
Rensselaer School, Tee, N. Y. Nov. 1826. 
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