There was only one mode of escaping such a danger or embarrassment as this, and that was, first, to arrive by repeated observation at an exact knowledge of the route followed by the stars across the sky, and of the rapidity of their march; secondly, to distinguish them one from another, to know each by its own name, to recognize its physiognomy, character, and habits. The first duty of the astrologer was to prepare such an inventory, and to discover the principle of these movements; then, and then only, would he be in a position to give a satisfactory answer to one asking where any particular star would be at the end of any specified number of days, weeks, or months. Thanks to such information, his client could fix upon some happy conjunction of the heavenly bodies, or at least avoid a moment when their influence would be on the side of disaster. In every undertaking of any importance the most favourable hour could be selected long before by the person chiefly concerned, the hour in which his star would be in the best quarter of the sky and in the most propitious relations with its neighbours. The phenomena produced in Chaldaea by these studies have been repeated more than once in the history of civilization; they embody one of those surprises to which humanity owes much of its progress. The final object of all this patient research was never reached, because the relations upon which a belief in its feasibility was based were absolutely chimerical, but as a compensation, the accessory and preliminary knowledge, the mere means to a futile end, have been of incalculable value. Thus, in order to give an imposing and apparently solid basis to their astrological doctrines, the Chaldaeans invented such a numeration as would permit really intricate computations to be made. By the aid of this system they sketched out all the great theories of astronomy at a very early age. In the course of a few centuries, they carried that science to a point never reached by the Egyptians.[93]