[44]Prin. Prop. xx Lib. Sec.
[45]With reference to the resisting power of the atoms.
[46]Prin. Lib. Tor. Prop, xxxix., also Prop, xli.
[47]In making this suggestion, the author is well aware that Ephemerides of the four chief asteroids have been given annually in the Greenwich Nautical Almanac; but for the object proposed they are utterly useless. Will any astronomer contend that these Ephemerides are true to ten seconds of arc? If not, they are useless for the purpose suggested above, and the theory wants revision. And it is evident that any objection against its practicability, founded on the uncertainty of the number of the asteroids themselves, as has already been urged in answer to this suggestion, is an evidence that the objector weighed the subject in the scales of his imagination only.
SECTION SIXTH.
THE POLAR ICE.
We shall conclude these pages by again referring to our theory of the weather, in connection with an event which every friend of humanity and every lover of natural science is bound deeply to deplore.
From the present position of the lunar nodes and apogee, the vortices of our earth do not ascend into very high latitudes. Now, according to the principles laid down, the frequency of storms tends to lower the temperature in the warm regions of the earth, and to elevate it in the polar regions. Let us suppose the northern limit of the vortices to be in latitude 70°. There will be, in this case, a greater prevalence of northerly winds within this circle of latitude, to supply the drain to the southward, and the back currents by passing above will descend at the pole, partaking of the temperature due to that elevation. The character of the arctic seasons may therefore be considered as partly dependent on the average direction of the wind. Suppose again, the extreme limits of the vortices to be about latitude 80°, the relative areas of the two circles are as 4 to 1; so that in this last case the exclusive range of the northerly winds is limited to one-fourth of the first area. South of 80° the wind will frequently come from the south, and by mixing with the local atmosphere of that latitude, will tend to ameliorate the small area to the northward. And the greater atmospheric commotion when confined to such a small circle of latitude, must assist materially to break up the polar ice; which would tend still more to equalize the temperature.
By referring to our table, we see that the mean conjunction of the pole of the lunar orbit and the moon’s apogee, was in longitude 128° on April 10, 1846, and let it be remembered that when the conjunction takes place due south or in longitude 270°, the vortices attain their greatest latitude north. When, on the contrary, the conjunction takes place due north or in longitude 90°,[48] the northern limits of the vortices are then in the lowest latitude possible.