Time and Its Measurement

Time as an abstraction. -- Ancient divisions of day and night. -- Night watches of the Old Testament. -- Quarter days and hours of the New Testament. -- Shadow or sun time. -- Noon mark dials. -- Ancient dials of Herculaneum and Pompeii. -- Modern Dials. -- Equation of time. -- Three historic methods of measuring time. -- "Time-boy" of India. -- Chinese clepsydra. -- Ancient weather and time stations. -- Tower of the winds, Athens, Greece.

Time, as a separate entity, has not yet been defined in language. Definitions will be found to be merely explanations of the sense in which we use the word in matters of practical life. No human being can tell how long a minute is; only that it is longer than a second and shorter than an hour. In some sense we can think of a longer or shorter period of time, but this is merely comparative. The difference between 50 and 75 steps a minute in marching is clear to us, but note that we introduce motion and space before we can get a conception of time as a succession of events, but time, in itself, remains elusive.

In time measures we strive for a uniform motion of something and this implies equal spaces in equal times; so we here assume just what we cannot explain, for space is as difficult to define as time. Time cannot be "squared" or used as a multiplier or divisor. Only numbers can be so used; so when we speak of "the square of the time" we mean some number which we have arbitrarily assumed to represent it. This becomes plain when we state that in calculations relating to pendulums, for example, we may use seconds and inches--minutes and feet--or seconds and meters and the answer will come out right in the units which we have assumed. Still more, numbers themselves have no meaning till they are applied to something, and here we are applying them to time, space and motion; so we are trying to explain three abstractions by a fourth! But, happily, the results of these assumptions and calculations are borne out in practical human life, and we are not compelled to settle the deep question as to whether fundamental knowledge is possible to the human mind. Those desiring a few headaches on these questions can easily get them from Kant and Spencer--but that is all they will get on these four necessary assumptions.

Evidently, man began by considering the day as a unit and did not include the night in his time keeping for a long period. "And the evening and the morning were the first day" Gen. 1, 5; "Evening and morning and at noonday," Ps. LV, 17, divides the day ("sun up") in two parts. "Fourth part of a day," Neh. IX, 3, shows another advance. Then comes, "are there not twelve hours in a day," John XI, 9. The "eleventh hour," Matt. XX, 1 to 12, shows clearly that sunset was 12 o'clock. A most remarkable feature of this 12-hour day, in the New Testament, is that the writers generally speak of the third, sixth and ninth hours, Acts II, 15; III, 1; X, 9. This is extremely interesting, as it shows that the writers still thought in quarter days (Neh. IX, 3) and had not yet acquired the 12-hour conception given to them by the Romans. They thought in quarter days even when using the 12-hour numerals! Note further that references are to "hours;" so it is evident that in New Testament times they did not need smaller subdivisions. "About the third hour," shows the mental attitude. That they had no conception of our minutes, seconds and fifth seconds becomes quite plain when we notice that they jumped down from the hour to nowhere, in such expressions as "in an instant--in the twinkling of an eye."

Before this, the night had been divided into three watches, Judges VII, 19. Poetry to this day uses the "hours" and the "watches" as symbols.

This 12 hours of daylight gave very variable hours in latitudes some distance from the equator, being long in summer and short in winter. The amount of human ingenuity expended on time measures so as to divide the time from sunrise to sunset into 12 equal parts is almost beyond belief. In Constantinople, to-day, this is used, but in a rather imperfect manner, for the clocks are modern and run 24 hours uniformly; so the best they can do is to set them to mark twelve at sunset. This necessitates setting to the varying length of the days, so that the clocks appear to be sometimes more and sometimes less than six hours ahead of ours. A clock on the tower at the Sultan's private mosque gives the impression of being out of order and about six hours ahead, but it is running correctly to their system. Hotels often show two clocks, one of them to our twelve o'clock noon system. Evidently the Jewish method of ending a day at sunset is the same and explains the command, "let not the sun go down upon thy wrath," which we might read, do not carry your anger over to another day. I venture to say that we still need that advice.

This simple line of steps in dividing the day and night is taken principally from the Bible because everyone can easily look up the passages quoted and many more, while quotations from books not in general use would not be so clear. Further, the neglect of the Bible is such a common complaint in this country that if I induce a few to look into it a little some good may result, quite apart from the matter of religious belief.

Some Chinese and Japanese methods of dividing the day and night are indicated in Fig. 1. The old Japanese method divides the day into six hours and the night also into six, each hour averaging twice as long as ours. In some cases they did this by changing the rate of the clock, and in others by letting the clock run uniformly and changing the hour marks on the dial, but this will come later when we reach Japanese clocks.

It is remarkable that at the present time in England the "saving daylight" agitation is virtually an attempt to go back to this discarded system. "John Bull," for a long period the time-keeper of the world with headquarters at Greenwich, and during that time the most pretentious clock-maker, now proposes to move his clocks backward and forward several times a year so as to "fool" his workmen out of their beds in the mornings! Why not commence work a few minutes earlier each fortnight while days are lengthening and the reverse when they are shortening?

This reminds me of a habit which was common in Scotland,--"keeping the clock half an hour forward." In those days work commenced at six o'clock, so the husband left his house at six and after a good walk arrived at the factory at six! Don't you see that if his clock had been set right he would have found it necessary to leave at half past five? But, you say he was simply deceiving himself and acting in an unreasonable manner. Certainly, but the average man is not a reasonable being, and "John Bull" knows this and is trying to fool the average Englishman.

Now, as to the methods of measuring time, we must use circumstantial evidence for the pre-historic period. The rising and the going down of the sun--the lengthening shadows, etc., must come first, and we are on safe ground here, for savages still use primitive methods like setting up a stick and marking its shadow so that a party trailing behind can estimate the distance the leaders are ahead by the changed position of the shadow. Men notice their shortening and lengthening shadows to this day. When the shadow of a man shortens more and more slowly till it appears to be fixed, the observer knows it is noon, and when it shows the least observable lengthening then it is just past noon. Now, it is a remarkable fact that this crude method of determining noon is just the same as "taking the sun" to determine noon at sea. Noon is the time at which the sun reaches his highest point on any given day. At sea this is determined generally by a sextant, which simply measures the angle between the horizon and the sun. The instrument is applied a little before noon and the observer sees the sun creeping upward slower and slower till a little tremor or hesitation appears indicating that the sun has reached his height,--noon. Oh! you wish to know if the observer is likely to make a mistake? Yes, and when accurate local time is important, several officers on a large ship will take the meridian passage at the same time and average their readings, so as to reduce the "personal error." All of which is merely a greater degree of accuracy than that of the man who observes his shadow.

The gradual development of the primitive shadow methods culminated in the modern sundial. The "dial of Ahas," Isa. XXXVIII, 8, on which the sun went back 10 "degrees" is often referred to, but in one of the revised editions of the unchangeable word the sun went back 10 "steps." This becomes extremely interesting when we find that in India there still remains an immense dial built with steps instead of hour lines. Figure 2 shows a pocket, or portable sundial taken from the ruins of Herculaneum and now in the Museo National, Naples. It is bronze, was silver plated and is in the form of a ham suspended from the hock joint. From the tail, evidently bent from its original position, which forms the gnomon, lines radiate and across these wavy lines are traced. It is about 5 in. long and 3 in. wide. Being in the corner of a glass case I was unable to get small details, but museum authorities state that names of months are engraved on it, so it would be a good guess that these wavy lines had something to do with the long and short days.

In a restored flower garden, within one of the large houses in the ruins of Pompeii, may be seen a sundial of the Armillary type, presumably in its original position. I could not get close to it, as the restored garden is railed in, but it looks as if the plane of the equator and the position of the earth's axis must have been known to the maker.

Both these dials were in use about the beginning of our era and were covered by the great eruption of Vesuvius in 79 A.D., which destroyed Pompeii and Herculaneum.

Modern sundials differ only in being more accurately made and a few "curiosity" dials added. The necessity for time during the night, as man's life became a little more complicated, necessitated the invention of time machines. The "clepsydra," or water clock, was probably the first. A French writer has dug up some old records putting it back to Hoang-ti 2679 B.C., but it appears to have been certainly in use in China in 1100 B.C., so we will be satisfied with that date. In presenting a subject to the young student it is sometimes advisable to use round numbers to give a simple comprehension and then leave him to find the overlapping of dates and methods as he advances. Keeping this in mind, the following table may be used to give an elementary hint of the three great steps in time measuring:

Shadow time, 2000 to 1000 B. C.

Dials and Water Clocks, 1000 B. C. to 1000 A. D.

Clocks and watches, 1000 to 2000 A. D.

I have pushed the gear wheel clocks and watches forward to 2000 A.D., as they may last to that time, but I have no doubt we will supersede them. At the present time science is just about ready to say that a time measurer consisting of wheels and pinions--a driving power and a regulator in the form of a pendulum or balance, is a clumsy contrivance and that we ought to do better very soon; but more on this hoped-for, fourth method when we reach the consideration of the motion on which we base all our time keeping.