SOI 
on Magnetic Attraction . 
present instance north *. Now, when the bar has this position, 
it will be parallel to the magnetic equator of the needle, and, 
therefore, wholly below that equator in one case, when, conse- 
quently, the dip end of the horizontal needle ought, according 
to the theory, to deviate towards it, and wholly above in the 
other, when the contrary end of the needle should deviate : 
when the compass is at the ends of the bar, this being in the 
equator, the needle would not be affected. Mr Lecount de- 
duces the properties of this instrument from all the observations 
which he has so diligently and carefully made in different mag- 
netic latitudes, and they are obviously the consequences of our 
theory ; I therefore think we may conclude, from this and the 
other facts of his to which I have adverted, that the theory 
which has afforded me so ready an explanation of these pheno- 
mena, and those observed by myself in this latitude, will prove 
equally consistent with those that may be observed in different 
parts of the Globe. I have now only to add a few observations on 
the connection between this hypothesis and the theory of electric 
currents. 
When I saw the first accounts of the electro-magnetic experi- 
ments of MM. Oersted and Ampere, which were not made till 
after my paper had been read, I did not consider that they 
would throw much light on the subject on which I had been 
engaged, as the connection between their experiments and mine 
appeared to be but remote. I however find, that the hypothesis 
which I had previously advanced, accords perfectly with the 
theory to which Ampere has been gradually led by his experi- 
ments. In these experiments, he appears to have been guid- 
ed by the soundest views, and certainly displays the greatest 
ingenuity in the construction of his apparatus, and skill in its 
management. As one result of his experiments on the elec- 
tric currents produced from the Voltaic pile, their actions on 
each other, on magnetised needles, and the action of the earth 
* Should this instrument, or any other, be found to answer the purpose of de- 
termining accurately the dip of the needle in all cases on board a ship, it would 
supply the most essential datum for the computation of the deviation of the hori* 
zontal needle, in all positions of the ship, in all parts of the earth. 
VOL, V. NO. 10 . OCTOBER 1891 . X 
