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correspond, for a considerable length of time, with that ofany effect produced by Jupiter , and cause au apparent,although not real, coincidence, with the period of lli years,which elapses between its Perihelion-passages. A sufficientlylong-continued series of observations would, however, dis-tinguish between the two classes of phenomena.
As to prophecies of impending trouble connected with thenear coincidence of the dates of the Perihelia which occurbetween 1880 and 1885, we most confidently believe that noone need regard them, although it is certainly somewhatremarkable that the dates should just now follow one anotherquite so rapidly. It is also an unfortunate fact for theprophets in question, that, Jupiter ’s period being barelytwelve years, that huge planet will be very nearly in itsAphelion , or at its greatest distance from the Sun , theposition of which is marked 1886 in Fig . XCIII., beforeSaturn will have reached its Perihelion in 1885. In 1885we might therefore expect the influence of Jupiter , and thatby far the most important of all such possible influences, to benearly reversed, and to oppose that of Saturn .
It may also be well to notice another important fact; viz.,that the change in the attractive effect of the Sun upon theEarth , in the course of each single year , is vastly greater thanthe change in the attractive effect, even of Jupiter , when itsPerihelion and Aphelion passages respectively draw it especiallynear to the Earth , or remove it to an unusual distance from it.This is, of course, upon our previous supposition, which we haveadopted for purposes of illustration, that the action referred totakes place according to the law by which gravity attracts. Sohuge is the Sun that a change of 3,000,000 miles in its dis-tance, at different times in the course of each year, alters itsattraction upon the Earth about 10,000 times as much, as achange of 46,000,000 miles of distance alters the average valueof that of Jupiter . It may also be calculated that the aunualchange in the Sun ’s attraction upon the Earth is about 1,800times as great as the whole average attraction of Jupiter .Hence we may easily conclude that, if the Perihelion-passageof Jupiter affects the Earth , the Earth ’s own Perihelion