Note 180 — Chapter III · CAMPAIGN AGAINST THE HELVETII. (Year of Rome 696.) (Book I. of the “Commentaries.”)

The Romans used little precision in the division of time. Forcellini (Lex., voce Hora) refers to Pliny and Censorinus. He remarks that the day—that is, the time between the rising and setting of the sun—was divided into twelve parts, at all seasons of the year, and the night the same, from which it would result that in summer the hours of the day were longer than in winter, and vice versa for the nights.—Galenus (De San. Tuend., VI. 7) observed that at Rome the longest days were equal to fifteen equinoctial hours. Now, these fifteen hours only reckoning for twelve, it happened that towards the solstice each hour was more than a quarter longer than towards the equinox. This remark was not new, for it is found in Plautus. One of his personages says to a drunkard: “Thou wilt drink four good harvests of Massic wine in an hour!” “Add,” replied the drunkard, “in an hour of winter.” (Plautus, Pseudolus, v. I, 302, edit. Ritschl.)—Vegetius says that the soldier ought to make twenty miles in five hours, and notes that he speaks of hours in summer, which at Rome, according to the foregoing calculation, would be equivalent to six hours and a quarter towards the equinox. (Vegetius, Mil., I. 9.)

Pliny (Hist. Nat., VII. 60) remarks that, “at the time when the Twelve Tables were compiled, the only divisions of time known were the rising and setting of the sun; and that, according to the statement of Varro, the first public solar dial was erected near the rostra, on a column, by M. Valerius Messala, who brought it from Catania in 491, thirty years after the one ascribed to Papirius; and that it was in 595 that Scipio Nasica, the colleague of M. Popilius Lænas, divided the hours of night and day, by means of a clepsydra or water-clock, which he consecrated under a covered building.”

Censorinus (De Die Natali, xxiii., a book dated in the year 991 of Rome, or 338 A.D.) repeats, with some additions, the details given by Pliny. “There is,” he says, “the natural day and the civil day. The first is the time which passes between the rising and setting of the sun; on the contrary, the night begins with the setting and ends with the rising of the sun. The civil day comprises a revolution of the heaven—that is, a true day and a true night; so that when one says that a person has lived thirty days, we must understand that he has lived the same number of nights.

“We know that the day and the night are each divided into twelve hours. The Romans were three hundred years before they were acquainted with hours. The word hour is not found in the Twelve Tables. They said in those times, ‘before or after mid-day.’ Others divided the day, as well as the night, into four parts—a practice which is preserved in the armies, where they divide the night into four watches.” Upon these and other data, M. Le Verrier has had the goodness to draw up a table, which will be found at the end of the volume, and which indicates the increase or decrease of the hours with the seasons, and the relationship of the Roman watches with our modern hours. (See Appendix B.)