It appears that the Chaldeans (Kaldai or Kaldi) were in the earliest times merely one out of the many Cushite tribes inhabiting the great alluvial plain known afterwards as Chaldea or Babylonia. In process of time as the Kaldi grew in power, their name prevailed over that of the other tribes inhabiting the country; and by the era of the Jewish captivity it had begun to be used generally for all the inhabitants of Babylonia. It had thus come by this time to have two senses, both ethnic: in the one, it was the special appellative of a particular race to whom it had belonged from the remotest times; in the other, it designated the nation at large in which the race was predominant. Afterwards it was transferred from an ethnic to a mere restricted sense, from the name of a people to that of a priest caste or sect of philosophers. The Kaldi proper belonged to the Cushite race. While both in Assyria and in Babylonia, the sernitic type of speech prevailed for special purposes, the ancient Cushite dialect was purely reserved for scientific and religious literature. This is no doubt the "learning" and the "tongue" to which reference is made in the Bible (Dan. I. 4). It became gradually inaccessible to the great mass of people who had emigrated by means, chiefly, of Assyrian influence. But it was the Chaldean learning in the old Chaldean or Cushite language. Hence all who studied it, whatever their origin or race, were, on account of their knowledge, termed Chaldeans. In this sense Daniel himself, "the master of Chaldeans" (Dan. V. 11.), would, no doubt, have been reckoned among them, and so we find Seleucas, a Greek, called a Chaldean by Strabo (XVI. 1, Sec. 6). The Chaldeans were really a learned class, who by their acquaintance with the language of science became its depositaries. They were priests, magicians or astronomers, as their preference for one or other of those occupations inclined them; and in the last of these three capacities they probably effected discoveries of great importance. The Chaldeans, it would appear, congregated into bodies forming what we may perhaps call universities, and they all engaged together in it for their progress. They probably mixed up to some extent astrology with their astronomy, even in the earlier times, but they certainly made great advance in astronomical science to which their serene sky and transparent atmosphere specially invited them. In later times they seem certainly to have degenerated into mere fortune-tellers (_vide_ Smith's Dict. of the Bible, Art. _Chaldeans_). In their practice of astromancy or enchanting the stars, and in pretending to overhear what passed in the heavens, they, the Jinns, used to sit on the tops of lofty mansions at night-time for hours offering sacrifices to the stars and enchanting them. In their peculiar tongue and learning they called this practice "stealing a hearing" and "sitting for listening" (Suras XV, verse 17, and LXXII, verses 8, 9).