he sphere, its
poles, axis, the equator, arctic and antarctic circles, equinoctial
points, solstices, colures, horizon, etc. No one competent to form an
opinion any longer entertained a doubt respecting the globular form of
the earth, the arguments adduced in support of that fact being such as
are still popularly resorted to--the different positions of the horizon
at different places, the changes in elevation of the pole, the phenomena
of eclipses, and the gradual disappearance of ships as they sail from
us. As to eclipses, once looked upon with superstitious awe, their true
causes had not only been assigned, but their periodicities so well
ascertained that predictions of their occurrence could be made. The
Babylonians had thus long known that after a cycle of 223 lunations the
eclipses of the moon return. The mechanism of the phases of that
satellite was clearly understood. Indeed, Aristarchus of Samos attempted
to ascertain the distance of the sun from the earth on the principle of
observing the moon when she is dichotomized, a method quite significant
of the knowledge of the time, though in practice untrustworthy;
Aristarchus thus finding that the sun's distance is eighteen times that
of the moon, whereas it is in reality 400. In like manner, in a general
way, pretty clear notions were entertained of the climatic distribution
of heat upon the earth, exaggerated, however, in this respect, that the
torrid zone was believed to be too hot for human life, and the frigid
too cold. Observations, as good as could be made by simple instruments,
had not only demonstrated in a general manner the progressions,
retrogradations and stations of the planets, but attempts had been made
to account for, or rather to represent them, by the aid of epicycles.

[Sidenote: Biography of the Ptolemies.]

It was thus in Alexandria, under the Ptolemies, that modern astronomy
arose. Ptolemy Soter, the founder of this line of kings, was not only a
patron of science, but likewise an author. He composed a history of the
campaigns of Alexander. Under him the collection of the library was
commenced, probably soon after the defeat of Antigonus at the battle of
Ipsus, B.C. 301. The museum is due to his son Ptolemy Philadelphus, who
not only patronized learning in his own dominions, but likewise
endeavoured to extend the boundaries of human knowledge in other
quarters. Thus he sent an expedition under his admiral Timosthenes as
far as Madagascar. Of th