Page:Popular Science Monthly Volume 11.djvu/286

272 effect, drawn away from the waters on the far side of her, and thus, the water being left behind, a tide is produced on this side, as well as on the side at which the force of gravity acts directly. That so great an absurdity could have been accepted so long by our writers of textbooks, is truly marvelous. It is, indeed, so contrary to all known facts and laws of physics that, if no other influence were felt by the waters at the far side of the earth than attraction, there would be just the opposite effect produced to that alleged by this absurd hypothesis. This can be demonstrated by actual experiment, and as conclusively as any other fact coming within the reach of experimental philosophy. It has been proved experimentally that all bodies on the surface of the earth at midnight are heavier than at any other hour of the twenty-four; and that when new moon occurs at midnight, this increase of weight or gravity felt by matter on this part of the surface of the earth is still greater. Now, if this theory were correct, attraction would produce just the opposite effect; that is, matter would weigh less at midnight than at other hours of the twenty-four. On the side of the earth facing the sun and moon, the weight of bodies is diminished, as it should be, according to the theory which I propose to establish in this article.

The truth of this fact is very easily accounted for. Suppose the earth were placed in such a position, in space, that she could not feel any of the sun's attraction, nor that of any other body. Then gravity would be equal on all parts of the earth's surface, on the supposition of its being a perfect sphere and at rest. But now bring her within the attractive influence of the sun. Then all particles of matter on the earth's surface most remote from the sun would feel the force of gravity of both the sun and the earth; and these two forces would act in the same direction and in the same straight line, directed through the centre of the earth to the centre of the sun. On the side facing the sun, these two forces would also act in the same straight line, but in opposite directions. Hence a decrease of weight on one side and an increase thereof on the opposite side of the earth. The same result follows between the earth and moon under a similar supposition. It is therefore not true that the least amount of attraction is felt by the waters of the earth at that part of her surface most remote from the sun or from the moon. It is indeed true that the sun and moon have less power of attraction on the particles of matter at this part of the earth's surface than they have on particles of matter facing them. But, as attraction diminishes as the square of the distance increases, this attractive force of these two bodies on any part of the earth's surface is not near so great as that of the earth herself on such part of her surface. Therefore, as these remote particles feel the attraction of sun and moon plus the attraction of the earth herself, they are drawn with greater force toward the centre of the earth than any other particles. Consequently, it cannot be true that the whole