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gives about ^ as the fraction which the Moon ’s weight is ofthat of the Earth .
By such various processes, the results of which agree sovery satisfactorily, is this important and interesting valuedetermined, so that we are able to state with the greatestpossible certainty that the Earth ’s weight is almost exactly8 If times that of the Moon . We may, on another occasion,attempt to show that we are even able to achieve the wondrousfeat of weighing some of the fixed stars, notwithstanding theiralmost inconceivable distance from us. At present let it sufficeto have explained that there are several independent methodsby which we can weigh the nearest of the heavenly bodies,albeit even that one, comparatively near as it is, is separatedfrom us by an interval which never falls short of 220,000miles.
Thus far we have spoken of the Moon ’s distance from theEarth and of its weight, and have only incidentally assumedthat it is the Earth ’s satellite, accompanying it in its annualjourney round the Sun. Our next attempt shall be to form asomewhat more accurate conception of the Moon ’s actual pathin space, while month by month it appears to us to circle roundthe Earth in the opposite direction to that in which the handsof a watch go round when we look at its face, or with arotation which is termed from west to east, and whichcorresponds in its direction with that of the Earth on itsaxis, and of the Earth and all the other planets in their orbitsround the Sun.
That this is the case may easily be seen, notwithstandingthat the axial rotation of the Earth from west to eastintroduces some little difficulty into the observation bymaking the Sun, Moon , and stars all apparently go roundthe sky from east to west in rather less than twenty-four hours.For if the Moon , while so appearing by this latter effect tomove from east to west, be carefully watched, it will benoticed that it is at the same time actually travelling fromwest to east amongst the stars with a speed which is of nosmall magnitude. If it be seen to be at a certain distance eastof some bright star at a given hour, one hour afterwards it will