at the rate of eight hundred and thirty-one miles an hour.[877] But if you will oppose the moon to the sun with respect to its size, its distance, and its course, you will find there is no comparison to be made between them. Remember that the diameter of the earth is nine thousand miles, that of the sun a hundred times more,[878] which gives nine hundred thousand miles;[879] now, if this be its width in every direction, judge what its superficies and volume must be. Can you comprehend the vastness of this extent, and that a million of such globes as the earth, all together, would not exceed the sun in size?[880] You will ask, then, how far is the sun from the earth, if one can judge of it by its apparent small size? You are quite right, the distance can hardly be conceived; for it is proved that the sunʼs distance from the earth can be no less than ten thousand times the diameter of the earth, or, in other words, than ninety millions of miles; it may be four times, perhaps six times, perhaps ten times as much, for ought we know; there is no method discovered to determine this distance.[881] Now, to assist you in understanding this, let us suppose a millstone falling from the sun upon the earth; let it come down with all swiftness imaginable, and even swifter than the heaviest bodies descend, falling from a very great height; let us also suppose that it always preserves the same swiftness, without increase or diminution; that it advances thirty yards every second, which is half the height of the highest steeple, and consequently, eighteen hundred yards in a minute; but to facilitate our computation, let us allow it two thousand six hundred and forty yards a minute, which is a mile and a half; its fall will then be three miles in two minutes, ninety miles in an hour, and two thousand one hundred and sixty miles in a day; now, it must fall ninety millions of miles before it comes down to the earth; so that it cannot be less than forty-one thousand six hundred and sixty-six days, which is more than one hundred and fourteen years before it can perform this journey. Let all this not frighten you, Lucilius; I will tell you more. The distance of Saturn from the earth is at least ten times as great as the sunʼs is; that is, no less than nine hundred millions of miles, and the stone would be above eleven hundred and forty years in falling down from Saturn to the earth.[882] Now, by this altitude of Saturn, exert your imagination, if you can, and conceive the immensity of its daily course; the circle which Saturn describes is above eighteen hundred millions of miles diameter, and consequently above fifty-four hundred millions of miles in circumference; so that a race-horse, if supposed to run thirty miles an hour, must be twenty thousand five hundred and forty-eight years in going this round.