milking-season approaches.... The camels are pregnant ‘in the tenth month’, and bring forth their young in February.” This statement is supported by the etymology. _Safar_ comes from a root with the meaning ‘to be empty’. Since two months appear between _safar_ and the cold season, the two months of _safar_ include the end of the dry and the beginning of the rainy season, before a more abundant vegetation has sprung up, and are therefore the worst period of lack of food. The root from which _jumada_ comes has the sense ‘to grow stiff’, which suits the time of the sharp cold. _Rabi_ as a season has a double sense, it is partly used to describe a period in autumn which is often identified with _charif_, the date-harvest, and partly to describe the pasture-season in spring. The explanation of this fact is doubtless that the word refers to the sprouting vegetation, the pasture-season, partly, indeed, to the vegetation which appears simultaneously with the autumn rains, but partly to the richer pasture which springs up with the increasing heat after the winter rains. Out of these three seasons, according to a familiar precedent, six months are made. They do not exactly cover the winter half of the year, but fall somewhat earlier, since the last month, _jumada II_, belongs to the cold period. As for the other months, the sense of _ramadan_, ‘the hot’, is certain, and it alludes to the warm season, in fact to its beginning, since _ramadan_ is the third month after _jumada II_. The attempted explanations of _sha’ban_ and _shawwal_ are all very uncertain. The other three names refer to festivals. In _rajab_ a festival was celebrated in all holy places, in which sacrifices of camels and sheep were offered up. The root means ‘to fear, to reverence’; the month is therefore called the ‘holy’, or the ‘deaf and dumb’, since the noise of weapons is stilled. The names of the last two months refer to the great pilgrimage to Mecca. _Dhu-l-qa’da_ is ‘the month of sitting’, and the explanation given for the name--that the month was so called because in it no expeditions or predatory excursions took place--is doubtless correct. It is the first month of the holy peace which prevails during the time of pilgrimage. The second month is named from the feast of pilgrims itself, _dhu-l-hijja_. CHAPTER IX. CALENDAR REGULATION. 1. THE INTERCALATION. The circumstance that the lunar months are among almost all peoples named from the phases of Nature involves the necessity of an agreement between the two really incommensurable periods given by the sun and the moon. This problem is the central point of the older scientific chronology. We shall now investigate more closely how the problem has arisen, and what has been its development among the primitive peoples.