THE EARTH. 



463 



ascertained by observing when and where the sun's diameter is least and 

 greatest. 



The diurnal rotation of the earth on its axis is a fact which all the world 

 are now so habituated to admit, and are taught so early, that few even think of the 

 necessity of asking for any demonstration of it ; and yet for thousands of years 

 this fundamental fact of astronomy was not only not admitted, but any one who 

 would have had the temerity to have asserted it, would have been deemed a fit 

 candidate for an asylum for insane persons. Such is the wonderful force of 

 habit. 



Let us, however, suppose ourselves ignorant of this fact, and that for the 

 first time we should be told that the place we dwell on and the ground on 

 which we walk is carried round the diameter passing through the poles of the 

 globe once in twenty-four hours ; that if we happen to be on or near the equa- 

 tor, we are thus whirled round at the rate of a thousand miles an hour, and that 

 at the latitude of forty to fifty degrees we should be transported at about half 

 that speed : it is surely conceivable that such an assertion heard for the first 

 time would excite very naturally astonishment and incredulity ; and although 

 habit has taught us to assent to it, reason must still suggest the question, 

 " What arguments have induced mankind to instil into the minds of the young 

 this principle as an indubitable fact ?" 



We direct our view to the firmament, and we see all the objects upon it rise 

 in the east and set in the west, the sun among the number. The stars pre- 

 serve their relative positions ; and, in short, all objects which appear in the 

 firmament move as though the motions did not belong to them, but as if the 

 whole firmament was carried round the earth every twenty-four hours with 

 a common motion, carrying all the bodies which appear upon it with that 

 motion. 



Now. there are two suppositions, either of which will with equal precision 

 explain this appearance ; and there is no other possible way, save these two, 

 by which it can be explained. 



It may either be produced as at the first view it appears to be by the 

 whole universe turning with a common motion every twenty-four hours round 

 the globe of the earth, or by the globe of the earth itself turning on its axis 

 once every twenty-four hours. How long mankind embraced by preference 

 the former supposition, will be rendered apparent by the very etymology of the 

 term universe* itself. Yet, to our apprehension, informed as we are of the 

 magnitudes, distances, and general structure, not of the solar system only, but 

 of the stellar universe, how eminently absurd does not such a supposition ap- 

 pear ! It would compel us to admit, not only that the stupendous globe of the 

 sun, nearly a million and a half times greater than that of the earth, revolves 

 every twenty-four hours round the earth at a distance of one hundred millions 

 of miles, but also that the planets, including Jupiter, fourteen hundred times, 

 and Saturn, one thousand times greater than the earth, the one at four hundred 

 millions of miles and the other at nine hundred millions of miles from the earth, 

 have also this inconceivable motion. But this is not all : we should be forced 

 to admit not only that the entire solar system whirls round the earth once a 

 day, but we should have to impute the same diurnal rotation to the countless 

 myriads of stars placed in regions of the universe so distant that light takes 

 several hundred years to come from them to the earth, moving at the rate of 

 two hundred thousand miles per second ; these stars, moreover, being suns, 

 many of them more stupendous than our"Wn ! It will be readily admitted that 

 such suppositions are invested with a degree of improbability amounting to 



* Universe, from UNUS, one ; and TERSUM, a THING TURNED : signifying to turn icilh one common 

 motion. 



