If we attempt to name in years the date of the commencement--not of astronomy itself--for that probably in some form was coeval with the race of man itself, but of recorded observations, we are met with a new difficulty arising from the various ways in which they reckoned time. This was in every case by the occurrence of the phases of one or other of the above-mentioned phenomena; sometimes however they selected the apparent rotation of the sun in twenty-four hours, sometimes that of the moon in a month, sometimes the interval from one solstice to the next, and yet they apparently gave to each and all of these the same title--such as _annus_--obviously representing a cycle only, but without reference to its length. By these different methods of counting, hopeless confusion has often been introduced into chronology; and the moderns have in many instances unjustly accused the ancients of vanity and falsehood. Bailly attempted to reconcile all these various methods and consequent dates with each other, and to prove that practical astronomy commenced "about 1,500 years before the Deluge, or that it is about 7,000 years old;" but we shall see reason in the sequel for suspecting any such attempt, and shall endeavour to arrive at more reliable dates from independent evidence. Perhaps the remotest antiquity to which we can possibly mount is that of the Aryans, amongst whom the hymns of the _Rig Veda_ were composed. The short history of Hebrew and Greco-Roman civilization seems to be lost in comparison with this the earliest work of human imagination. When seeking for words to express their thoughts, these primitive men by the banks of the Oxus personified the phenomena of the heavens and earth, the storm, the wind, the rain, the stars and meteors. Here, of course, it is not practical but theoretical astronomy we find. We trace the first figuring of that primitive idea alluded to before--the heaven above, the earth below. Here, as we see, is the earth represented as an indefinite plane surface and passive being forming the foundation of the world; and above it the sky, a luminous and variable vault beneath which shines out the fertile and life-giving light. Thus to the earth they gave the name P'RTHOVI, "the wide expanse;" the blue and star-bespangled heavens they called VARUNA, "the vault;" and beneath it in the region of the clouds they enthroned the light DYAUS, _i.e._ "the luminous air." [Illustration: FIG. 1.] From hence, it would appear, or on this model, the early ideas of all peoples have been formed. Among the Greeks the name for heaven expresses the same idea of a hollow vault ([Greek: koilos], hollow, concave) and the earth is called [Greek: ge], or mother. Among the Latins the name _coelum_ has the same signification, while the earth _terra_ comes from the participle _tersa_ (the dry element) in contradistinction to _mare_ the wet.