Experience teaches the peoples who have only a twelve-month series that this is not sufficient: so we are told of the Mandan and Minnetaree that they have generally recognised that the year has more than twelve months[877]. When the intercalary month, as among certain Indians, is named ‘the lost month’[878], this points to the fact that it is an addition to a twelve-month series, just as in Babylonia, where the same method of expression recurs[879]. The Masai have twelve months[880]. The great rains cease with _loo-’n-gokwa_, which is named from the evening setting of the Pleiades. Should the rains still continue at the beginning of the following month, the Masai say:--“We have forgotten, this is _loo-’n-gokwa_.” Should the hot season not be over at the beginning of the month following _ol-oiborare_, they say:--“We have forgotten, this is _ol-oiborare_”[881]. It is clear that if through the dead reckoning the months are advanced in relation to the seasons, one month will be repeated, i. e. intercalated. The preceding month is forgotten. Thus the necessity for modifying the series of months is felt, and in response to this an empirical intercalation arises. When this intercalation is left to itself, conflicting opinions, as we have already seen, arise as to it. An end is made to these disputes and order is established when the decision is placed in the hands of definite persons. This was done among the Jews, the regulation of whose calendar affords a particularly plain example of this empirical intercalation, which, out of religious conservatism, they kept until well into the post-Christian period, in fact until the necessities of the Dispersion compelled, from the second century, a mitigation of the original rules, and finally at an uncertain period, perhaps not until medieval times, led to a calculated regulation. According to the Talmud the appearance of the crescent of the new moon was determined by deposition before a court of justice of three members. After that the beginning of the month was signalised in the country in earlier times by fires, later by couriers. A suitable intercalation was absolutely necessary for the celebration of the feasts, since at the Feast of the Passover on the 14th of Nisan the first-fruits of the corn were offered, and the two other great feasts were also of an agrarian character. For this purpose the court of justice visited the fields. If they saw that the crops were not yet ripe at the Passover time, and that the fruits also were not so far advanced as they were accustomed to be at this time of the year, they intercalated a month in accordance with these two signs: if only one of these signs was to be observed the decision was made to depend on other minor circumstances[882]. By way of example I give an official document of Rabbi Gamaliel II, issued to the inhabitants of Judaea, Galilaea, and the Dispersion at the date 90-110 A. D.[883]. “We make known to you that the lambs are small and the young of the