His division was according to their trades, and consisted of the musicians, the goldsmiths, the builders, the dyers, the shoemakers, the carriers, the coppersmiths, and the potters. All the other trades he united into one guild. He assigned to each trade its special privileges, common to all the members, and arranged that each should have its own times of meeting, and worship its own special patron god, and by this means he did away with that habit, which hitherto had prevailed among the citizens, of some calling themselves Sabines, and some Romans; one boasting that they were Tatius's men, and other Romulus's. So this division produced a complete fusion and unity. Moreover he has been much praised for another of his measures, that, namely, of correcting the old law which allows fathers to sell their sons for slaves. He abolished this power in the case of married men, who had married with their father's consent; for he thought it a monstrous injustice that a woman, who had married a free man, should be compelled to be the wife of a slave. XVIII. He also dealt with astronomical matters, not with perfect accuracy, and yet not altogether without knowledge. During the reign of Romulus the months had been in a state of great disorder, some not containing twenty days, some five-and-thirty, and some even more, because the Romans could not reconcile the discrepancies which arise from reckoning by the sun and the moon, and only insisted upon one thing, that the year should consist of three hundred and sixty days. Numa reckoned the variation to consist of eleven days, as the lunar year contains three hundred and fifty-four days, and the solar year three hundred and sixty-five. He doubled these eleven days and introduced them every other year, after February, as an intercalary month, twenty-two days in duration, which was called by the Romans Mercedinus. This was a remedy for the irregularities of the calendar which itself required more extensive remedies. He also altered the order of the months, putting March, which used to be the first month, third, and making January the first, which in the time of Romulus had been the eleventh, and February the second, which then had been the twelfth. There are many writers who say that these months, January and February, were added to the calendar by Numa, and that originally there had only been ten months in the year, just as some barbarians have three, and in Greece the Arcadians have four, and the Acarnanians six. The Egyptians originally had but one month in their year, and afterwards are said to have divided it into four mouths; wherefore, though they live in the newest of all countries, they appear to be the most ancient of all nations, and in their genealogies reckon an incredible number of years, because they count their months as years.