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The Flinders papersletters and documents about the explorer Matthew Flinders (1774-1814)
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Loose pages from Flinders' private letterbook (6 of 6). Letters to Charles Desbassayns on financial matters and magnetic research. (FLI04) Page 5

equator it differs from 2° to 9°; taking the poles at the same distances from the
center but under the points on the surface deduced from the imperfect va-
reations ^ above mentioned, two of the is my six observations come exact, two differ 3° and the
other two 6° so that I am not satisfied as to the exact position.
      Mr {Haüy}concludes that the magnetic power sum of the magnetic
attractions and repulsions ^ are every where the same but I judge with M.M. H and B that it
augments from the ^ magnetic equator to the poles, in ^ about the proportion 2002 to 2032
but it is the difference of power between the one pole and the other that
most interests me, [illegible] since it varies with
each change of place, the dip and causes inclination being produced by the of the needle, and the changes of va-
^ riation on ship board. I have tried exercised my little knowledge to arrive at this directly,
by means of the inclination alone, and thence to deduce the place
of the poles from the observations, but have been obliged to assume
give that up, and assume places for the poles to try whether the incli-
nation obtained therefrom agreed with the observations; and since the
calculations are rather long, the time and trouble ^ a number of these essays have
given me, are considerable.
      The position of the poles so near the center of the earth is certain-
ly very different to that of the poles of an artificial magnet, but
I do not conceive it necessary to conclude from thence that there is
a magnet lodged in the center. The earth is a heterogeneous mass
containing many isolated magnetic substances, each of which has
its particular poles; these poles form amongst them a common
center for each species of attraction, and which, as in gravity, will
be at the center of all the masses combined; so that could we annihi- change
late half the magnetic substances in one hemisphere into non-mag-
netic, the ^ mean points of magnetic attractions poles, according to my idea, would retreat into the both
center in the other hemisphere. I have remarked an effect on ship board which illustrate
this: a ship as containing various isolated magnetic substances, is
^ in this respect analogous to the earth. My observations shew the attraction of effects
of the attractive point in the ^ Investigator ship to have ^ been greater in the northern
hemisphere than in the south at the same dip; but during the passage I removed two guns
^ and some other iron from the after part of the ship forward, by which ^ it appears I judge the com-
mon centers of the attractions on board was removed further from the
binnacle, and the power ^ of the upper point on the compass, confined to that of the poles
upon it became thereby lessened in the proportion, as the observations

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Flinders, Matthew
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