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diurnal variation of the magnetic needle, &c. 
from the sun’s passage : so that the ?iorth pole, to the north 
of the equator, would always have the sun nearly on its 
meridian ; the south pole to the north of the equator would 
probably be nearly in the longitude 130° east from this meri¬ 
dian : and corresponding to these, a south and a north pole 
would be developed to the south of the equator. Supposing 
then that the place of greatest heat on the equator is in 
general 45® to the east of the sun, the poles of greasest 
intensity would be developed in the longitude of about 45° 
west, and those of least intensity in the longitude of about 
85° east from the place of heat. The situation however of 
the place of heat, and the distances of the poles from it, must 
be greatly influenced by the nature of that part of the earth 
to which the sun is vertical. For there can be no doubt, that 
if, during the passage of the sun over the scorched desarts of 
Africa, the place of greatest heat is in general 45° behind the 
sun, the border of that continent on the west will continue 
the place of greatest heat, for some time after the sun has 
advanced 45° over the Atlantic ; and that on the other hand, 
the eastern shores of the continent of America will become 
more heated than the Atlantic, even when the sun has 
scarcely passed the aquatic meridians. Besides this, owing 
to the different conducting powers of land and water, the 
intensities of the poles, and likewise their distances from the 
place of heat, may vary according as that place is on the land 
or on the water. Since then, when the sun is in the northern 
tropic, it passes over the greatest extent of land without 
intervening sea, and afterwards of sea scarcely intersected by 
land; and that the case is the reverse when it is in the 
southern tropic; this would produce a considerable effect on 
