than twenty-eight to the number of days in a lunation) and thirteen (almost as near an approach as twelve to the number of months in a year) do not. It seems to me highly probable that the date to which all inquiries into the origin of the constellations and the zodiacal signs seems to point--viz. 2170 B.C.--was the date at which the Chaldæan astronomers definitely adopted the new system, the lunisolar instead of lunar division of the zodiac and of time. One of the objects which the architects of the Great Pyramid (not the king who built it) may have had was not improbably this--the erection of a building indicating the epoch when the new system was entered upon, and defining in its proportions, its interior passages, and other features, fundamental elements of the new system. The great difficulty, an overwhelming difficulty it has always seemed to me, in accepting the belief that the year 2170 B.C. defined the beginning of exact astronomy, has been this, that several of the circumstances insisted upon as determining that date imply a considerable knowledge of astronomy. Thus astronomers must have made great progress in their science before they could select as a day for counting from, the epoch when the slow reeling motion of the earth (the so-called precessional motion) brought the Pleiades centrally south, at noon, at the time of the vernal equinox. The construction of the Great Pyramid, again, in all its astronomical features, implies considerable proficiency in astronomical observation. Thus the year 2170 B.C. may very well be regarded as defining the introduction of a new system of astronomy, but certainly not the beginning of astronomy itself. Of course we may cut the knot of this difficulty, as Prof. Smyth and Abbé Moigno do, by saying that astronomy began 2170 B.C., the first astronomers being instructed supernaturally, so that the astronomical Minerva came into full-grown being. But I apprehend that argument against such a belief is as unnecessary as it would certainly be useless.