THE TURNING OF THE* MRTH -101 



less sphere, with the stars set in its surface, and that the whole 

 sphere was wheeling round an invisible axis of which this one 

 fixed star was the extremity. 



It was from such a mental image that the Greeks gave to this 

 radial point of the skies their word for a pivot, vrwAws and so 

 we have Polaris, our pole-star. All this must have been noted 

 very anciently, for in the construction of his pyramid, from 

 four to six thousand years ago, Cheops had, as we have seen, 

 oriented his colossal tomb towards the pivot of the heavens of 

 his day. 



Later on, when the idea of the globular form of the earth 

 grew into acceptance, among astronomers at least, and the 

 beginnings of a climatology and geography were made, they 

 came in their poetical way to dress this globe in " zones," or 

 girdles ; the circle described by the sun at its northern solstice 

 was the boundary of one ; that described at the southern 

 station, of the other ; and as it was at the edges of this belt 

 that the sun seemed to turn back, they named the boundary 

 line the " tropics," the same as our word trope, or turn. Mid- 

 way between the two, they noted that the sun in its revolution 

 described a great circle of this globe, and when it was at this 

 point, the days and nights were equal all over the earth ; 

 whence they gave this great circle the name of the equant, or 

 equator. It must have puzzled the early observers vastly to 

 know why the sun should thus shift up and down in the sky. 

 Their puzzling must have deepened when they made a further 

 step. The planes, they noted, formed by these circles, were 

 parallel one to the other, and a line drawn through their centres, 

 and perpendicular to them, passed through the centre of the 

 earth; projected into space, it pointed straight to the pole- 

 star. In a word, it seemed as if the earth had an axis like the 

 heavens, and this seeming axis of the earth and the seeming 

 axis of the skies were one. Here was something to ponder. 



Of course, so long as they had no mortal idea of the distance 

 of the sun and stars, they had no trouble in believing that it 

 was the sun and the crystal sphere of the stars which moved. 

 But very early some penetrating mind must have struck in with 

 the thought that this motion might be explained another way 

 that the daily revolution of the sun, the nightly wheeling of the 

 stars, was the effect of the slow turning of the earth, and that 

 the sphere of the sky stands still. Just as on a very large 



