Stargazing: past and present . estars that were just visible on the southern horizon, whenculminating, gradually disappeared below it. These ob-servations were at once seized on, and Anaximanderaccounted for them by supposing that the earth was acylinder.^ The idea of a sphere did not come till later;when it did come then came the circle as an astrono-mical instrument. For let us consider that a personon the earth stands, say, at the equator; then he willjust be able to see along his north and south horizonthe stars pointed to by the axis of the globe : if nowhe is transported northwards, his
Stargazing: past and present . estars that were just visible on the southern horizon, whenculminating, gradually disappeared below it. These ob-servations were at once seized on, and Anaximanderaccounted for them by supposing that the earth was acylinder.^ The idea of a sphere did not come till later;when it did come then came the circle as an astrono-mical instrument. For let us consider that a personon the earth stands, say, at the equator; then he willjust be able to see along his north and south horizonthe stars pointed to by the axis of the globe : if nowhe is transported northwards, his horizon will change ^ Anaximander flourished about 547 CHAP. THE DAWN OF STARGAZING. with liim; lie will no longer be able to see the southernstars, but the northern ones will gradually rise above hishorizon till he gets to the north pole, when the northpole star, instead of being on his horizon, as was the casewhen he was at the equator, will be over his head. Soby moving from the equator to the pole (or a quarter of. Fig. 2. —The Zodiac of Dendcrali. the distance round the earth) the stars have moved fromthe horizon to the point overhead, or the zenith, thatis also a quarter of a circle. So it appears that if anobserver moves to such a distance that the stars appearto move over a certain division of a circle with referenceto the horizon, he must have moved over an equal 8 STARGAZING: PAST AND PRESENT. [book i. division on the earths surface. Then, as now, the circlein the Western world Avas divided into 360, so that theobserver in moving 1° by the stars would have movedover -ffiir of the distance round the earth, on the assump-tion that the earth is a globe ; and if the distance overwhich the observer has moved be multiplied by 360,the result will be the distance round the earth. Now let us see how Posidonius a long time afterwards(he was born about 135 years ) applied this con-ception. He observed that at Rhodes the star Canopusgrazed the horizon at culminati
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