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the earth and the sun, it may act not only by reflecting and 
absorbing a portion of the light and heat which would other- 
wise reach the earth, but also by altering the direction of the 
lines of magnetic force. The changes of temperature at the 
surface of the earth will thus be due partly to differences in 
the amount of heat received from the sun, and partly to 
changes in the movements of the great currents of the air 
produced by alterations in the earth’s magnetic condition. If 
the larger part of the difference of temperature is due to the 
latter mode of action, we might expect that during the 
warmer half of the period, the mean direction of the wind at 
any given station would be sensibly different from that during 
the cooler half ; and also, that the epochs of maximum and 
minimum temperature would not be the same at all parts of 
the earth’s surface. Both of these conclusions are borne out 
by the results given in the paper. Thus at St. Petersburg 
in 1859 the mean direction of the wind on maximum days 
was S. 54° W., and on minimum days S. 73° W. at 19° more 
to the west of South ; and at Sitka, on the north west coast 
of North America, in 1851, the mean direction on maximum 
days was S. 32° W., and on minimum days S. 56° W., the 
difference being 24°. As striking instances of the differences 
in the epochs at distant stations, it may be stated that in 
1859 'the epoch of maximum at St. Petersburg corresponded 
precisely with the epoch of minimum at Madras ; and that 
at Pekin, in 1851, the epoch of minimum was exactly coin- 
cident with the epoch of maximum at Sitka. 
Changes in the amount of heat received from the sun 
sufficient to produce the variations of temperature observed 
at any given station would no doubt affect the movements of 
the great currents of the atmosphere, though not to the 
extent indicated by the observations ; but it is difficult to 
conceive that they could produce the differences in the epochs 
which are found to take place. We may therefore fairly 
conclude that the action of the supposed ring of nebulous 
