The use of the twenty-eight-day period naturally suggested the division of time into weeks of seven days each. The ordinary lunar month is divided in a very obvious manner into four equal parts by the lunar aspects. Every one can recognise roughly the time of full moon and the times of half moon before and after full, while the time of new moon is recognised from these two last epochs. Thus the four quarters of the month, or roughly the four weeks of the month, would be the first time-measure thought of;--after the day, which is the necessary foundation of all time measures. The nearest approach which can be made to a quarter-month in days is the week of seven days; and although some little awkwardness arose from the fact that four weeks differ appreciably from a lunar month, this would not long prevent the adoption of the week as a measure of time. In fact, just as our years begin on different days of the week without causing any inconvenience, so the ancient months might be made to begin with different week-days. All that would be necessary to make the week measure fairly well the quarters of the month, would be to start each month on the proper or nearest week-day. To inform people about this, some ceremony could be appointed for the day of the new moon, and some signal employed to indicate the time when this ceremony was to take place. This--the natural and obvious course--we find was the means actually adopted, the festival of the new moon and the blowing of trumpets in the new moon being an essential part of the arrangements adopted by nations who used the week as a chief measure of time. The seven days were not affected by the new moons so far as the nomenclature of these days, or special duties connected with any one of them, might be concerned.