ALDUS TO THE READER, GREETINGS.

I have long since decided to benefit the studious in whatever way I can. Therefore, it seemed very useful to say something here about the days—which are divided into twenty-four parts—and those divided into twelve, and also about the hours as they are found in Palladius. This is all the more necessary because they are understood by very few men of our age. There are two kinds of days: some natural, some civil. Natural days, which we use everywhere now, consist of twenty-four equal parts from one sunset to another, which are called hours and, in Greek ἰσημεριναί equinoctial, are called equinoctial in Latin. Civil days, however, from sunrise to sunset, consist of twelve unequal parts, which are called καιρικαί temporal/seasonal in Greek, and in Latin are named "temporal," or—which is the same thing—"vulgar." These twelve parts are shortest at the winter solstice, being one-third smaller than the equinoctial hours, but at the summer solstice they are longest and one-third larger than the others. Consequently, they exceed the winter hours by two-quarters, or—what is the same—by half. Virgil wished to signify this in the verse: Unless you add a new star to the slow months, original: "An ne nouum tardis sydus te mēsibas addas." that is, June and July, in which the hours are longest. But in spring, when the sun enters Aries, and in autumn, when it enters Libra, they are equal to the equinoctial hours. From the winter solstice to the summer, they grow as the day grows, and from the summer to the winter, they decrease as it decreases. And since individual civil days and nights of the entire year are contained by twelve hours, the sixth hour of the day is always noon. It begins at sunrise and ends at sunset. For example, in the month of March, when these temporal hours are almost equal to the equinoctial hours, the first hour of the civil day is the same as the thirteenth hour of the natural day; the second is the same as the fourteenth; the third with the fifteenth; the fourth with the sixteenth; the fifth with the seventeenth; the sixth with the eighteenth; the seventh with the nineteenth; the eighth with the twentieth; the ninth with the twenty-first; the tenth with the twenty-second; the eleventh with the twenty-third; the twelfth with the twenty-fourth. Therefore, that statement in the Holy Scriptures: And from the sixth hour until the ninth, there was darkness over the whole earth, original: "A sexta autē hora usq; ad Nonam, tenebræ factæ sunt super uniuersam terram" must be understood as from the eighteenth hour until the twenty-first of the natural day, as hours are counted now. For among the ancients, sundials were divided into temporal, not equinoctial, hours of both night and day. In the month of June, however, when the hours are at their longest, the first temporal hour is the same as the ninth with one-third of the tenth equinoctial hour; the second is the remainder of the tenth with two-thirds of the eleventh; the third is the twelfth with one-third of the eleventh. And thus, every three temporal hours...