Originally the idea may have been to have festivals and sacrifices at the time of new moon, first quarter, full moon, and third quarter; but this arrangement would naturally (and did, as we know, actually) give way before long to a new moon festival regulating the month and seventh-day festivals, each class of festival having its appropriate sacrifices and duties. This, I say, was the natural course. Its adoption _may_ have been aided by the recognition of the fact that the seven planets of the old system of astronomy might conveniently be taken to rule the days and the hours in the way described in the essay on astrology. That that nomenclature and that system of association between the planets and the hours, days, and weeks of time-measurement was eventually adopted, is certain; but whether the convenience and apparent mystical fitness of this arrangement led to the use of weekly festivals in conjunction with monthly ones, or whether those weekly festivals were first adopted in the way described above, or whether (which seems altogether more likely) both sets of considerations led to the arrangement, we cannot certainly tell. The arrangement was in every way a natural one; and one may say, considering all the circumstances, that it was almost an inevitable one. There was, however, another possible arrangement, viz., the division of time into ten-day periods, three to each month, with corresponding new moon festivals. But as the arrival of the moon at the _thirds_ of her progress are not at all so well marked as her arrival at the quarters, and as there is no connection between the number ten and the planets, this arrangement was far less likely to be adopted than the other. Accordingly we find that only one or two nations adopted it. Six sets of five days would be practically the same arrangement; five sets of six for each month would scarcely be thought of, as with that division the use of simple direct observations of the moon for time measurement, which was the real aim of all such divisions, would not be convenient or indeed even possible for the generality of persons. Few could tell easily when the moon is two-fifths or four-fifths full, whereas every one can tell when she is half-full or quite full (the requisite for weekly measurement); and it would be possible to guess pretty nearly when she is one-third or two-thirds full, the requisite for the tridecennial division.