There is a difference of opinion at the present day amongst astronomers as to the time in which the planet Venus rotates upon her axis. This difference arises through the difficulty of perceiving or identifying any markings on her brilliantly lighted surface. She is probably continually cloud-covered, and the movements of the very faint shadings that are sometimes seen upon her have been differently interpreted. The older observers concurred in giving her a rotation period of 23^h 21^m, which is not very different from that of the earth. Many astronomers, amongst them Schiaparelli, assign a rotation period of 225 days, that is to say the same period as that in which she goes round the sun in her orbit. The axis on which she rotates is almost certainly at right angles to the plane in which she moves round the sun, and she has no moon.

We do not know if the planet is inhabited by intelligent beings, but assuming the existence of such, it will be instructive to inquire as to the conditions under which they must live if this view be correct, and the rotation period of Venus, and her revolution period be the same.

Venus would then always turn the same face to the sun, just as our moon always turns the same face to us and so never appears to turn round. Venus would therefore have no "days," for on her one hemisphere there would be eternal light, and on the other eternal darkness. Since she has no moon, she has no "month." Since she moves round the sun in a circle, and the axis through her north and south poles lies at right angles to her ecliptic, she has no "seasons," she can have no "year." On her daylight side, the sun remains fixed in one spot in the sky, so long as the observer does not leave his locality; it hangs overhead, or near some horizon, north, south, east, or west, continually. There are no "hours," therefore no divisions of time, it might be almost said no "time" itself. There are no points of the compass even, no north, south, east or west, no directions except towards the place where the sun is overhead or away from it. There could be no history in the sense we know it, for there would be no natural means of dating. "Time" must there be artificial, uncertain and arbitrary.

On the night side of Venus, if her men can see the stars at all for cloud, they would perceive the slow procession of stars coming out, for Venus turns continually to the heavens—though not to the sun. Mazzaroth would still be brought out in his season, but there would be no answering change on Venus. Her men might still know the ordinances of heaven, but they could not know the dominion thereof set upon their earth.This imaginary picture of the state of our sister planet may illustrate the fourteenth verse of the first chapter of Genesis:—

The making of the calendar is in all nations an astronomical problem: it is the movements of the various heavenly bodies that give to us our most natural divisions of time. We are told in Deuteronomy:—

This is the legitimate use of the heavenly bodies, just as the worship of them is their abuse, for the division of time—in other words, the formation of a calendar—is a necessity. But as there are many heavenly bodies and several natural divisions of time, the calendars in use by different peoples differ considerably. One division, however, is common to all calendars—the day.

The "day" is the first and shortest natural division of time. At present we recognize three kinds of "days"—the sidereal day, which is the interval of time between successive passages of a fixed star over a given meridian; the apparent solar day, which is the interval between two passages of the sun's centre over a given meridian, or the interval between two successive noons on a sundial; and the mean solar day, which is the interval between the successive passages of a fictitious sun moving uniformly eastward in the celestial equator, and completing its annual course in exactly the same time as that in which the actual sun makes the circuit of the ecliptic. The mean solar days are all exactly the same length; they are equal to the length of the average apparent solar day; and they are each four minutes longer than a sidereal day. We divide our days into 24 hours; each hour into 60 minutes; each minute into 60 seconds. This subdivision of the day requires some mechanical means of continually registering time, and for this purpose we use clocks and watches.

The sidereal day and the mean solar day necessitate some means of registering time, such as clocks; therefore the original day in use must have been the apparent solar day. It must then have been reckoned either from sunset to sunset, or from sunrise to sunrise. Later it might have been possible to reckon it from noon to noon, when some method of fixing the moment of noon had been invented; some method, that is to say, of fixing the true north and south, and of noting that the sun was due south, or the shadow due north. Our own reckoning from midnight to midnight is a late method. Midnight is not marked by the peculiar position of any visible heavenly body; it has, in general, to be registered by some mechanical time-measurer.

In the Old Testament Scriptures the ecclesiastical reckoning was always from one setting of the sun to the next. In the first chapter of Genesis the expressions for the days run, "The evening and the morning," as if the evening took precedence of the morning. When the Passover was instituted as a memorial feast, the command ran—

And again, for the sabbath of rest in the seventh month—

The ecclesiastical "day" of the Jews, therefore, began in the evening, with sunset. It does not by any means follow that their civil day began at this time. It would be more natural for such business contracts as the hiring of servants or labourers to date from morning to morning rather than from evening to evening. Naturally any allusion in the Scriptures to the civil calendar as apart from the ecclesiastical would be indirect, but that common custom was not entirely in agreement with the ecclesiastical formula we may perhaps gather from the fact that in the Old Testament there are twenty-six cases in which the phrases "day and night," "day or night" are employed, and only three where "night" comes before "day." We have a similar divergence of usage in the case of our civil and astronomical days; the first beginning at midnight, and the second at the following noon, since the daylight is the time for work in ordinary business life, but the night for the astronomers. The Babylonians, at least at a late date in their history, had also a twofold way of determining when the day began. Epping and Strassmaier have translated and elucidated a series of Babylonian lunar calendars of dates between the first and second centuries before our era. In one column of these was given the interval of time which elapsed between the true new moon and the first visible crescent.

It may be mentioned that the days as reckoned from sunset to sunset, sunrise to sunrise, and noon to noon, would give intervals of slightly different lengths. This would, however, be imperceptible so long as their lengths were not measured by some accurate mechanical time-measurer such as a clepsydra, sandglass, pendulum, or spring clock.

The first obvious and natural division of the whole day-interval is into the light part and the dark part. As we have seen in Genesis, the evening and the morning are the day. Since Palestine is a sub-tropical country, these would never differ very greatly in length, even at midsummer or midwinter.

The next subdivision, of the light part of the day, is into morning, noon and evening. As David says in the fifty-fifth Psalm—

None of these three subdivisions were marked out definitely in their beginning or their ending, but each contained a definite epoch. Morning contained the moment at which the sun rose; noon the moment at which he was at his greatest height, and was at the same time due south; evening contained the moment at which the sun set.

In the early Scriptures of the Old Testament, the further divisions of the morning and the evening are still natural ones.

For the progress of the morning we have, first, the twilight, as in Job—

Then, daybreak, as in the Song of Solomon—

where the reference is to the cool breezes of twilight. So too in Genesis, in Joshua, in the Judges and in Samuel, we find references to the "break of day" (literally, the rising of the morning, or when it became light to them) and "the dawning of the day" or "about the spring of the day." The progress of the morning is marked by the increasing heat; thus as "the sun waxed hot," the manna melted; whilst Saul promised to let the men of Jabesh-Gilead have help "by that time the sun be hot," or, as we should put it, about the middle of the morning.

Noon is often mentioned. Ish-bosheth was murdered as he "lay on a bed at noon," and Jezebel's prophets "called on the name of Baal from morning even unto noon."

We find the "afternoon" (lit. "till the day declined") mentioned in the nineteenth chapter of the Judges, and in the same chapter this period is further described in "The day draweth toward evening (lit. is weak)," and "The day groweth to an end" (lit. "It is the pitching time of the day," that is to say, the time for pitching tents, in preparation for the nightly halt).

As there was no dividing line between the morning and noontide, neither was there any between the afternoon and evening. The shadows of the night were spoken of as chased away by the cool breezes of the morning, so the lengthening shadows cast by the declining sun marked the progress of the evening. Job speaks of the servant who "earnestly desireth the shadow;" that is to say, the intimation, from the length of his own shadow, that his day's work was done; and Jeremiah says, "The shadows of the evening are stretched out." Then came sundown, and the remaining part of the evening is described in Proverbs: "In the twilight, in the evening, in the black and dark night."

In a country like Palestine, near the tropics, with the days not differing extravagantly in length from one part of the year to another, and the sun generally bright and shining, and throwing intense shadows, it was easy, even for the uneducated, to learn to tell the time of day from the length of the shadow. Here, in our northern latitude, the problem is a more complex one, yet we learn from the Canterbury Tales, that Englishmen in the time of the Plantagenets could read the position of the sun with quite sufficient accuracy for ordinary purposes. Thus the host of the Tabard inn, though not a learned man—

In the latter part of the day there is an expression used several times in Exodus, Leviticus, and Numbers "between the two evenings" which has given rise to much controversy. The lamb of the Passover was killed in this period; so also was the lamb of the first year offered daily at the evening sacrifice; and day by day Aaron was then commanded to light the seven lamps and burn incense. It is also mentioned once, in no connection with the evening sacrifice, when the Lord sent quails to the children of Israel saying, "At even (between the two evenings) ye shall eat flesh." In Deuteronomy, where a command is again given concerning the Passover, it is explained that it is "at even, at the going down of the sun." The Samaritans, the Karaite Jews, and Aben Ezra held "the two evenings" to be the interval between the sun's setting and the entrance of total darkness; i. e. between about six o'clock and seven or half-past seven. A graphic description of the commencement of the sabbath is given in Disraeli's novel of Alroy, and may serve to illustrate this, the original, idea of "between the two evenings."

In later times, on account of ritualistic necessities, a different interpretation was held. So Josephus says: "So these high-priests, upon the coming of their feast which is called the Passover, ... slay their sacrifices, from the ninth hour till the eleventh."[279:1] And the Talmud made the first evening to begin with the visible decline of the sun and the second with sunset, or "the two evenings" to last from three till about six. Schiaparelli gives the first evening from sunset until the time that the newly visible lunar crescent could be seen in the twilight sky, or about half an hour after sunset, and the second evening from that until darkness set in, basing his argument on the directions to Aaron to light the lamps "between the two evenings," since, he argues, these would not be made to burn in the daylight. Probably in the days of Moses and Aaron the period could not be defined as accurately as this would imply, as the opportunity of seeing the new moon could only come once a month, and we have no evidence of any mechanical time-measurer being then in use with them.

For shorter spaces of time we have the word "moment" or "instant" many times mentioned. The words may mean, the opening or winking of the eye, "the twinkling of an eye," spoken of by St. Paul, in his Epistle to the Corinthians, and do not describe any actual duration of time, or division of the day.

The only time-measurer mentioned in the Bible is the dial of Ahaz, which will form the subject of a later chapter. It need only be noted here that, as it depended upon the fall of the shadow, it was of use only whilst the sun was shining; not during cloudy weather, or at night.

As the day had three main divisions, so had also the night. There were three "watches," each, like the watches on ship-board, about four hours in length. So in the Psalms, "the watches" are twice put as an equivalent for the night.

The ancient Hebrews would have no difficulty in roughly dividing the night into three equal parts, whenever the stars could be seen. Whether they watched "Arcturus and his sons,"—the circumpolar constellations moving round like a vast dial in the north—or the bringing forth of Mazzaroth, the zodiacal constellations, in the south, they would soon learn to interpret the signs of night with sufficient accuracy for their purpose.

The first watch of night is mentioned in the book of Lamentations.

It was "in the beginning of the middle watch; and they had but newly set the watch," that Gideon and his gallant three hundred made their onslaught on the host of the Midianites.

It was in the third, the morning watch, that "the Lord looked unto the host of the Egyptians through the pillar of fire and of the cloud, and troubled the host of the Egyptians" as they pursued Israel into the midst of the Red Sea. In this watch also, Saul surprised the Ammonites as they besieged Jabesh-Gilead, and scattered them, "so that two of them were not left together."

In the New Testament, the Roman method of dividing the night is adopted; viz. into four watches. When the disciples were crossing the Sea of Galilee in their little boat, and they had toiled all night in rowing because the wind was contrary, it was in "the fourth watch of the night" that Jesus came unto them.

There is no mention of any mechanical time-measurer in the Old Testament, and in only one book is there mention in the English version of the word "hour." Five times it is mentioned in the Book of Daniel as the rendering of the Chaldean word sha‘ah, which literally means "the instant of time."

No mention either is made of the differing lengths of the days or nights throughout the year—at midsummer the day is 14-1/4 hours long, and the night 9-3/4. Job speaks, however, of causing "the day-spring to know its place," which may well refer to the varying places along the eastern horizon at which the sun rose during the course of the year. Thus in mid-winter the sun rose 28° south of the east point, or half a point south of E.S.E. Similarly in midsummer it rose 28° north of east, or half a point north of E.N.E.[282:1]

The Babylonians divided the whole day interval into twelve kasbu, or "double hours." Those again were divided into sixty parts, each equal to two of our minutes; this being about the time that is required for the disc of the sun to rise or set wholly. The Babylonian kasbu was not only a division of time, but a division of space, signifying the space that might be marched in a kasbu of time. Similarly we find, in the Old Testament, the expression "a day's journey," or "three days' journey," to express distance, and in the New Testament we find the same idea applied to a shorter distance in the "sabbath-day's journey," which was about two miles. But the Jews in New Testament times adopted, not the Babylonian day of twelve hours, but the Egyptian of twenty-four. So we find, in the parable of the Labourers in the Vineyard, mention made of hiring early in the morning, and at the third, sixth, ninth, and eleventh hours; and since those hired latest worked for but one hour, it is evident that there were twelve hours in the daylight. Our Lord alludes to this expressly in the Gospel according to St. John, where he says—

"Are there not twelve hours in the day? If any man walk in the day, he stumbleth not, because he seeth the light of this world. But if a man walk in the night, he stumbleth, because there is no light in him."