102 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXVII.) 
we assume the region to be somewhat in advance of it, the latter would be in that place 
where it could exert its maximum eastening effect; and therefore after that, as it 
recedes westwards, would let the needle return from east to west, as it does, following 
it. The needle continues to go west, passing its mean place for the month about 7^; 
in the meantime, before that, at a little after 6 o’clock, the sun has left the western 
segment by passing the magnetic equator; it has not yet set to Greenwich, and if it 
have any action, it will, because of the segment it is now in (2979.), still be to carry 
the needle end westward. The end in fact continues to go westward, slowly only, after 
10 o’clock, gaining a little from 10^ to 15^; and then, as the sun comes up, passing 
more rapidly west, as it ought to do, until 19'’, and finally making the great swing to 
the east as before. The whole progression here is very simple, and apparently a 
natural result of the assumed cause. Effects of cooling no doubt come in ; but the 
cold region has diminished in intensity and extent (3006.), has retreated northward, 
and its action appears in combining with the former to produce only variations in the 
velocity of the change. 
3023. Then for the winter, let us consider January ; and, as the eastening is a 
maximum in all the months at 1 o’clock, after the sun’s passage across the meridian, 
let us begin the cycle there. At l'’ the upper end of the needle is at extreme east, 
and the amount of the variation not half what it was in summer, the sun being now 
far off. The sun and warm region pass the magnetic meridian about 21'’ or 22'*; 
and therefore, in the hours before and after that, should produce the full west to 
east effect. At 1 o’clock the needle returns west, following the retreating sun, and 
does so quickly for seven or eight hours, or up to 9'’, during which time the warm re- 
gion, and also the early morning cold region, are in quadrants and positions, which, 
if they have any action at all like that referred to in the experiments (2975. 2995.), 
would then set or hold the needle end west of its mean position. Then an action 
of the following kind supervenes; the needle remains stationary until 11'’, after 
which it goes east at midnight and until 15'’; again remains stationary, or nearly 
so, for two hours ; then eastens again, slowly at first and afterwards more rapidly, 
until l'’, when it has attained its maximum eastening and the place from whence it 
set out. 
3024. This night action is another case of the action of a cold region like that 
considered in respect of St. Petersburgh (3010.). It appears to me that at 11'’ the 
immediate sun action and returns west after it, were over; that the cold region which 
was coming round from the east did then act by its paramagnetic condition (com- 
bined with the complementary effects of the sun’s action on the other side of the 
globe), and set the needle eastward, as it would be competent to do (2994. 3010.) 
until 14*’ or 15'’. In eastening, the needle does not arrive at the mean place, but is 
still l' west of it ; and the reason why it hangs there from 15'’ to 17'’ and then begins to 
go east again, more and more under the sun’s action, is probably that, as the sun 
rises in the southern tropics, his distance and position bring the resulting distant 
