THE PLANETS URANUS AND NEPTUNE.

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\Y e are willing to allow all this, and not only so, hut inaddition, that, in the year 1880, the Earth did also happen topass between Jupiter aud the Sun most remarkably near tothe time of Jupiter ’s passage through its Perihelion, viz., withineleven days ; and yet we see no necessity for believing thatany special influence must, under such circumstances, arise,—certainly not that any harmful results must ensue.

We must, moreover, recollect that we have no idea-, if anysuch action should take place, by what law it would be governed.It might be proportional to the mass of the body so actingdivided by its distance; or divided by that distance squared,or cubed. It might follow laws similar to those of electricity,or of magnetism ; or it might simply act according to theordinary law of gravitation. If the latter be the case (a pos-sible, although not a very probable, supposition, which wemay use for the purpose of illustration as a mean betweenvarious imaginable laws), we may calculate, that the maximumattractive effect of Jupiter upon the Earth would be nearlyfourteen times that of Saturn, Saturn ’s about thirty-threetimes that of Uranus , and that of Urauus more than twicethat of Neptune ; so that (speaking approximately) Jupiter ’smaximum influence would approach 500 times that of Uranus ,and exceed 1,000 times that of Neptune .

We may also remark, that not only do the great distancesof Neptune and Urauus from the Earth almost put themout of the question altogether, but the very near approach ofNeptune ’s orbit to a circular form makes its Perihelion-passageutterly unimportant. If any Perihelion effects exist, they mustpractically be limited to those of Jupiter and of Saturn ; audJupiter is so much the more important, both in mass andproximity, that all we should think it necessary to do to settlethe question (and this may be worth the while), is carefullyto compare meteorological records, and to see whether anyperiodic change can be detected which corresponds with thedates of Jupiter 's Perihelion-passages.

At the same time, it must be remembered, that the period ofSun-spot maxima and minima (see Lecture II., p. 37) hks anaverage duration of about 11 - 1 years, and might therefore