As a rule the institution of the sabbath appears to be primarily due to moon-worship, a form of worship which seems to have been almost universal. With all deference to the opinion of that school which fancies it can trace a solar myth in almost every tradition and folklore tale, we think that moon-worship was and is much more general than sun-worship, and for the simple reason that the regular daily recurrence of the sun is far less likely to excite speculation and wonder in uncivilized man than the varying phases and periodical disappearance and reappearance of the moon.
We imagine that the earliest moon sabbath was a monthly festival, held on the day when the new moon was first seen. The Mendis of Sierra Leone abstain from all work on the day of the new moon, alleging that if they infringed this rule the corn and rice would grow red, the day of the new moon being a "day of blood," from which we may perhaps infer that human sacrifices were once offered to the new moon. The Bechuanas of South Africa also observe the day of twenty-four hours, from the appearance of the new moon at sunset till next evening, as a day of rest, and the people refrain from going to their gardens. Neither the Mendis nor the Bechuanas have subdivided the lunar month into weeks, so here we have examples of peoples who reckon time by lunar months and observe a monthly moon sabbath.
If we suppose this to be the first stage, and the lunar month to be subsequently divided into weeks, then it follows that the first day of the first week will be the festival or sabbath of the new moon, as was the case in Sofala. Then, because the first day of the first week is a moon sabbath, it will naturally happen in some cases, through a connection of ideas, that the first day of each week will be dedicated to the moon, and the moon sabbath will recur as often in the month as the latter contains weeks. We have evidence of this among the Tshi and Gã tribes, among whom moon-worship is no longer found, except in so far that the new moon is always saluted with reverence, but that it used to prevail is shown by the moon's epithet Bohsŭm, holy, sacred, or deity. Dyo-da, the name of the first day of the Tshi week, means "day of rest," in the sense of a general day of rest for all people, for the moon was worshiped by all classes, and not, like the gods of the sea and agriculture, by special sections of the community only. Dyo-da was a day of rest for everybody, while Bna-da was only a day of rest for seafaring folk and Fi-da for husbandmen. Dsu, the name of the first day of the Ga week, means "purification," and because it was sacred to the moon Dsu seems to have become a title of the moon, for in the cognate Yoruba and Ewe languages we find the moon called Osu and Dsunu respectively, and in Ga itself the word silver is rendered by dsu-etei,