Account of Captain Seoresby’s 
count of the principal discoveries detailed in these papers, in or- 
der to bring into one point of view subjects of very considerable 
practical importance. In addition to the articles that are already 
before the public on this subject, we have had the opportunity 
of witnessing some of Mr Scoresby’s experiments, and of examin- 
ing his magnetical apparatus, and we are therefore enabled to 
communicate some particulars that have not hitherto been laid be- 
fore the public. 
Mr Scoresby’s attention was first directed to the investigation 
of the magnetic laws, in consequence of a series of experiments 
undertaken by him in the years 1815 and 1817, for determining 
the cause of the u deviation of the compass** on ship-board. In 
trying the magnetic properties of different masses of iron about 
the ship’s deck, he found, what, indeed, was long before known 
to be the fact, that, in the high northern latitudes, all rods of 
iron, in a vertical position, were magnetical, while the same rods 
placed nearly horizontal, exerted little or no influence on the 
compass. The result of his inquiries into the law of the mag- 
netic action was such as might have been expected, namely, that 
ferruginous substances became magnetical by position, the upper 
parts, as respects the plane of the magnetic equator intersecting 
them through the centre of gravity, acquiring south polarity, 
and the lower parts north polarity. But while this law seems 
universally to prevail,, it exhibits an apparent modification by 
experiment, in the case of slender bars or thin plates of iron ; 
for these bodies, when placed in the magnetic plane, exhibit no 
magnetic action on a compass ; because the magnetic axis in 
them corresponding with their shortest axis, the two poles are 
so near together that they neutralize each other, with respect to 
their effects upon the compass. 
As the magnetic plane may be readily discovered by experi- 
ment., with slender bars of iron free from permanent magnetism, 
Mr Scoresby constructed an instrument, called a Magnetimeter , 
with which the exact angle where the polarity of iron disap- 
pears may be determined ; and this he finds gives him the com- 
plement of the dip, with such a degree of accuracy as in most 
respects to answer the ends of a dipping-needle. 
64 For examining into the phenomena of the polarity of iron 
arising from position, &c.> I constructed, (says he) about the 
month of December 1 819, an apparatus, of which, with improve- 
