88 THE WORLD MACHINE 



slight that, looked at between thumb and forefinger held at 

 arm's length, the fingers nearly close is this a body so vast 

 that it would almost cover the then known world ? a body 

 whose height or diameter is equal to the entire length of the 

 Mediterranean, which cost the mariners in their vessels a fort- 

 night or more to traverse. And this colossus of the skies swings 

 free in space ! It clearly revolves about the earth ! What 

 holds it in its place ? He to whom all this came first would 

 doubt the validity of his own computations ; he would be 

 unable to realise that such a thing could be. 



And yet, as he reflected, conviction must have come. In 

 climbing mountains, whence, in a clear atmosphere, objects 

 are visible a long way, he must have noted how, at a distance, 

 huge edifices sink away to a point ; a great city, even, becomes 

 a patch. But, ascending even the highest mountains, the moon 

 draws no nearer. Compared with its elevation above the earth, 

 the height of the tallest peaks seems nothing. Certainly it 

 must lie afar off ; and if this is true, the simplest of calculations 

 enforces the belief that its bulk is vast beyond belief. Appear- 

 ances had again been overthrown. 



It remained to consider the problem of the sun. If the 

 eye may be so deceived as to the grandeur of the moon, to what 

 conceptions of immensity must the imagination rise to picture 

 the extent and distance of the monarch of the day ? 



Here again simple geometrical considerations suificed to 

 establish the groundwork of a just estimate. The sun lies 

 behind the moon : the eclipses showed that ; and it must be 

 far behind, because the shadow cast by the earth is a diminishing 

 cone, and the sun is therefore larger than the earth. If it were 

 smaller, the conical shadow would be divergent. The earth, 

 they had found, was three or four times in diameter the size 

 of the moon ; the sun must therefore be at least six or eight 

 times. And yet, averaging the various eclipses, the moon in 

 transit just about covers the disk of the sun ; their apparent 

 size is the same. 



A body which is eight times another in diameter and yet 

 appears to be the same in size, is eight times as far away. If 

 the moon is distant about sixty earth radii, the sun must, there- 

 fore, be distant at least four or five hundred earth radii. It must 

 be at least two million miles away ! How the world was growing ! 



