(2) De La Rue specially studied the spots observed at the times when the planets Venus and Mars were at a heliocentric distance from the Earth equal to 0, 90, 180, and 270 degrees, and arrived at this result; the spots are larger in the part of the Sun which is away from Venus and Mars, and they are smaller on the side on which these planets happen to be. The same result was obtained, whether Carrington’s figures or the Kew photographs were employed. (3) Meanwhile it does not appear that Jupiter emits any similar influence. This influence should be easily perceived, for if we calculate the action of the planets in the way that we calculate the tides, treating it as directly proportional to the masses and inversely proportional to the cubes of the distances, the influence of Jupiter should greatly outweigh that of Venus. Wolf thought that he had noticed traces of some influence being exerted by Saturn; but this remains altogether without confirmation. De La Rue noticed that large spots are generally situated at extremities of the same diameter. This law also often applies to the development of large prominences. The coincidence agrees well with the theory that there exists on the Sun some action resembling that of our tides. Whatever may be the amount of probability which attaches to these explanations we ought not to forget that we are still far off from possessing the power of giving a vigorous demonstration of them. If we consider with attention the periodical variations of the spots we shall not be long in coming to the conclusion that it is impossible to connect them directly with any one astronomical function in particular, for the spots appear in a sudden and irregular manner which contrasts in a striking degree with the continuous and progressive action of the ordinary perturbations which we meet with in the study of Celestial Mechanics. There is but one reply possible to this objection. The spots and their changes must be visible manifestations of the periodical activity of the Sun—an activity which itself depends (as assumed) on the action of the planets and on their relative positions. The cause, thus defined, of the Sun’s activity may be very regular; the activity itself may vary in a continuous manner without the resulting phenomena possessing the same continuity and the same regularity. We see this in the periodical succession of the Seasons on the Earth. The position of the Sun, and consequently its manner of acting upon our globe, varies with a remarkable uniformity, but nevertheless the meteorological phenomena which result are irregular and capricious. Thus it comes about that physicists are more and more inclined to believe that the spots are only secondary effects produced by causes more important and more fundamental.