192 Mr. Flinders on certain Differences 
and that this point is nearly in the center of the ship where the 
shot are deposited, for here the greatest quantity of iron is col- 
lected together. 
2d. I suppose this point to be endued with the same kind of 
attraction as the pole of the hemisphere where the ship is ; 
consequently, in New Holland the south end of the needle 
would be attracted by it and the north end repelled. 
3d. That the attractive power of this point is sufficiently 
strong in a ship of war to interfere with the action of the mag- 
netic poles upon a compass placed upon or in the binnacle. 
If these suppositions are consistent with the laws of mag- 
netism, established by experiments, I judge that they will 
account for all the differences above noticed ; for the interfe- 
rence will necessarily be most perceptible upon a compass 
when the attractive point is at right angles to the magnetic 
meridian, that is, when the ship’s head is east or west, and will 
altogether vanish or become imperceptible when the attractive 
point and meridian coincide, or when the ship’s head is north 
or south. That the power of this point should become less as 
the ship increases her distance from the magnetic pole has not 
indeed entered into my suppositions ; but it may probably be 
true, and is indeed almost a necessary consequence of the 
second supposition. If the above hypothesis, so to call it, be 
true, it must follow, that the differences in the variation of the 
magnetic needle, arising from a change in the ship’s head, 
ought to be directly contrary to those before recited, when the 
ship is on the north side of the magnetic equator, for the 
north point of the needle should then be attracted, and 
the south end repelled. I have no observations which are very 
decisive upon this head, but those that were taken on board 
