14 Improvement in manufacturing Magnetic Needles. 
of matter as were here removed, is still hypothetical, while 
strong electric and magnetic powers are known to 
comitant products of this apparatus, is it not the most reason- 
able supposition, that this transfer of matter from the posi- 
tive to the negative pole was the effect of one or both of these 
agents exerting their appropriate power of attraction? It is 
well known, from the experiments of Sir H. Davy, that the 
two poles are opposite in a very high degree, that is, one is 
strongly positive and the other strongly negative, and both 
therefore are in a condition to exert the strongest electrical . 
attractions. Or if it were ascertained that the poles were in 
opposite magnetic states, and strongly excited, this fact would 
be sufficient to account for the transfer of matter which took 
place. In the present state of our knowledge, it is more rea- 
sonable to ascribe the effect to the attraction of one or the 
other of these ugents, or to both of them acting conjunctive- 
ly, than to a current which transports the particles of matter 
by its mechanical action. In the one case, we employ in the 
explanation, causes which are known to exist and to be ade- 
quate ; in the other case, we adduce a cause which is purely 
hypothetical. 
(To be continued.) 
ART. 1L—Improvement in the manufacture of Magnetic 
Needles. By Prof. Amos Eek = 
TO PROF. SILLIMAN. 
SEVERAL years of the early part of my life were devoted 
to an extensive land agency, among the western and north- 
ern spurs of ytskill mountains. During this period, I 
ran most of the outlines of two hundred thousand acres, be- 
sides four ink a across this Alpine district. The 
difficulties to which I was almost daily subjected, by the ir- 
regularity of the magnetic needle, were often very embarrass- 
ing. he old surveyors of that time assured me, that these 
fits, as they denominated those irregularities, were produced 
by the action of magnetic ores, which they believed abounded 
in this mountainons district t one time I entertained the 
opinion, that I had collected facts sufficient to demonstrate, 
* 
