Centrifugal force and gravitation : a lecture / by John Harris.

  • Harris, John, 1942 May 3-
Date:
1873
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Licence: Public Domain Mark

Credit: Centrifugal force and gravitation : a lecture / by John Harris. Source: Wellcome Collection.

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    tlie side next to her, and draws it tioni tlie earth towards Jicr, and in addition attracts the earth itself, and (h-aws that also from the water on the opposite side; thus accounting for the high tide at both sides ; but if such were the case the earth and moon would soon come together; because, if tiie larger body,—the earth, deviates i'rom her orbit to approach the moon, the lesser body,—th moon, must deviate so m,ichthe more (in inverse propor- tion to the mass) to approacli the earth; and,as this approx- imation is supposed to be continuous, the result would necessarily bo, within a certain limited time, contact be- tween the earth and the moon. The hypothesis, that the water is drawn towards the moon at the side opposite to her, does not when attentively considered appear to be tenable ; no reason is shown why such an effect should be confined to the water only; tiie air would be proportion- ately subject to the same action ; and solids on the earth's surface also; vanations in the barometnc level and in pendulum vibrations would indicate and measure such a partial and local effect of the moon's gravitating influence. Such a cause operating in tlie slightest imaginable degree, in the maimer supposed, would have the effect of accumu- lating all the water on the earth's surface, in that part exposed to the moon's direct influence. Moreover the sun's attraction is supposed to operate in the same manner. Page 79 (Drew^s Astmwmy). Not only is the moon an agent in producing tides, but the sun also ; in conse- quence, hov ever, of his greater distance his attraction is not so mu'.h felt; the whole force of attraction being in compouiid proportion of the mass directly and the distance squared inversely. The force of attraction thus deduced The hypothesis is negatived by the fact that the influ- ence of the solar gravitation on the earth's surface is the same by night as by day. Substances, whei-ier solid or fluid, weigh the same at midnight as at midday whereas if the hypothesis were sound there would necessarily be a difTerence, and the apparent gravity of each thing on the (. ;,