At the close of each “great year,” called by Aristotle—according to Censorinus—the _greatest_, and which consists of six _sars_[96] our planet is subjected to a thorough physical revolution. The polar and equatorial climates gradually exchange places; the former moving slowly toward the Line, and the tropical zone, with its exuberant vegetation and swarming animal life, replacing the forbidding wastes of the icy {31} poles. This change of climate is necessarily attended by cataclysms, earthquakes, and other cosmical throes.[97] As the beds of the ocean are displaced, at the end of every decimillennium and about one neros, a semi-universal deluge like the legendary Noachian flood is brought about. This year was called the _Heliacal_ by the Greeks; but no one outside the sanctuary knew anything certain either as to its duration or particulars. The winter of this year was called the Cataclysm or the Deluge,—the Summer, the Ecpyrosis. The popular traditions taught that at these alternate seasons the world was in turn burned and deluged. This is what we learn at least from the _Astronomical Fragments_ of Censorinus and Seneca. So uncertain were the commentators about the length of this year, that none except Herodotus and Linus, who assigned to it, the former 10,800, and the latter 13,984, came near the truth.[98] According to the claims of the Babylonian priests, corroborated by Eupolemus,[99] “the city of Babylon, owes its foundation to those who were saved from the catastrophe of the deluge; _they were the giants_ and they built the tower which is noticed in history.”[100] These giants who were great astrologers and had received moreover from their fathers, “the sons of God,” every instruction pertaining to secret matters, instructed the priests in their turn, and left in the temples all the records of the periodical cataclysm that they had witnessed themselves. This is how the high priests came by the knowledge of the _great_ years. When we remember, moreover, that Plato in the _Timæus_ cites the old Egyptian priest rebuking Solon for his ignorance of the fact that there were several such deluges as the great one of Ogyges, we can easily ascertain that this belief in the _Heliakos_ was a doctrine held by the initiated priests the world over. The Neroses, the Vrihaspati, or the periods called yugas or kalpas, are life-problems to solve. The Satya-yug and Buddhistic cycles of chronology would make a mathematician stand aghast at the array of ciphers. The Maha-kalpa embraces an untold number of periods far back {32} in the antediluvian ages. Their system comprises a kalpa or grand period of 4,320,000,000 years, which they divide into four lesser yugas, running as follows: 1st.—Satya-yug 1,728,000 years. 2d.—Trêtya yug 1,296,000 “ 3d.—Dvâpa yug 864,000 “ 4th.—Kali yug 432,000 “ ——————— Total 4,320,000