Time Telling through the Ages

Now the sky itself is like a great bowl or inverted hemisphere, and, howsoever the sun moved upon it, the shadow would move in the same way upon the inside of the bowl or hemisphere. And by drawing lines in the bowl, similar to the lines of longitude upon the map, the hours could be correctly measured. The "Hemicycle of Berosus," as it was called, remained in use for centuries and was the favorite form of sun-dial all through the classic period of Greece and Rome. Cicero had one at his villa near Tusculum, and one was found, in 1762, at Pompeii.

But the hemicycle was not easy to make unless it were fairly small, and, if small, it was not very easy to read. You can see that a shadow which traveled only a few inches in a whole day would move so slowly that one could hardly see it go. And the shadow of a round ball is not a clear sharp-pointed thing like the hand of a watch, whose exact position can be seen however small it may be. Besides, the ancients were not very particular about exact timekeeping. They had no trains to catch, and in their leisurely lives convenience counted for more than doing things "on the minute." So they still continued using the upright pointer which the Greeks called the gnomon, meaning "the one who knows."

"Cleopatra's Needle," and other Egyptian obelisks may also have been used as huge gnomons to cast their shadows upon mammoth dials, for they were dedicated to the sun. With an object of such great size the shadow would move rapidly enough to be followed easily by the eye. But of course its motion would be irregular because of the flat surface of the dial. The word "dial," by the way, comes from the Latin dies meaning "day," because it determined the divisions of the day.

Then there was applied the idea of making the shadow move over a hollow space, such as a walled courtyard, going down one side, across, and up the other side as the sun went up, across and down the sky. Sometimes light was used instead of shadow, the place being partially roofed over and a single beam of light being admitted through a small hole at the southern end. Men kept track of the motion of this beam as it touched one point after another during the day.

Do you remember the miracle of the dial of Ahaz, mentioned in the Bible? Hezekiah the king was sick and despondent, and would not believe that he could ever recover from his illness or prevail against his enemies. So the prophet, Isaiah, in an effort to comfort the royal sufferer, made the shadow return backward ten degrees upon the dial of Ahaz, as a sign from heaven that his prophecy of the king's future recovery was true. You will find the story in Isaiah, Chapter thirty-eight.

This dial of Ahaz was probably a curved flight of steps rising like the side of a huge bowl at one end of the palace courtyard, with either a shadow cast by a pointer overhead or a beam of light admitted through an opening. It can be seen that this and similar great dials were applications of the hemicycle idea on a large scale.

According to our chronology, the dial of Ahaz must have been built during the eighth century, B. C. Although the sun-dial period was, of course, many hundreds of years older than this, yet the story of this Hebrew king and prophet is the first authentic reference to a sun-dial which has been discovered.

However, the final improvement of the dial was made when it was discovered that by slanting the pointer, or gnomon, exactly toward the north pole of the sky – the point where the north star appears at night – the sun's shadow could be cast upon a flat surface with accurate results in indicating time.

This may sound simple, but if you will look at a sun-dial such as may still be found in gardens, you will see that the lines of the hours and minutes are laid out on certain carefully calculated angles; you will realize that people had to acquire considerable knowledge before they were capable of making such calculations. The whole subject of dial-making is so complicated that, in 1612, there was published a big book of eight hundred pages on the subject.

The angles of the lines of the sun-dial must be different for different latitudes. It took that strong-arm race of ancient times, the Romans, a hundred years to learn this fact. The Romans, at this time, were developing their civilization from the shoulders downward, while the Greeks and some of the Greek colonies developed theirs from the shoulders upward. Rome was a burly power, with powerful military muscles. Whatever it wanted it went out and took at the point of the sword, as some nations have endeavored to do in latter days. Thus, the city of Rome became a vast storehouse of miscellaneous loot – the fruit of other men's brains and hands.

Some conqueror of that day took back with him a sun-dial from the Greek colony of Sicily. This was set up in Rome, where nobody realized that even the power of Rome's armies was not able to transplant the angle of the sun as it shone upon Sicily far to the southward. It was nearly one hundred years before these self-satisfied robbers found that they had been getting the wrong time-record from the stolen instrument. Thus, the original owners had a form of belated revenge, could they but have known it.

One of the largest of all the sun-dials was the one set up by the Roman Emperor Augustus when he returned from his Egyptian wars bringing with him an obelisk not unlike the one which now stands near the Metropolitan Museum of Art in Central Park, New York City. If you can imagine this Egyptian obelisk, with its strange hieroglyphic characters upon its four sides, surrounded by a great dial with the figures of the hours marked upon its surface, you will get an idea of the size of this huge timepiece. However, it was probably more picturesque than valuable as a time-keeper.

There is an important difference between clocks and sun-dials, aside from the self-evident one of the difference in their construction. Clock-time is based on what is called "mean time." If we study the almanac table of times of sunrises and sunsets, and count the number of hours from sunrise of one day to sunrise of the next, we find it is rarely exactly twenty-four hours, but usually a few minutes more or less, while the average for the whole year is twenty-four hours. The clock is constructed to keep uniform time based on this average length of day.

The sun-dial time marks "apparent time," the actual varying length of each day. The sun-dial time, therefore, is nearly always some minutes ahead or behind that of a clock, the greatest discrepancy being about sixteen minutes for a few days in November. There are, however, four days in the year when the clock and the sun-dial agree perfectly in the time they indicate. These days are April 15th, June 15th, September 1st, and December 24th.

When in the eighteenth century clocks and watches began to come into wide-spread use sun-dials fell into neglect, except as an appropriate bit of ornament in gardens. At Castletown, in the Isle of Man, is a remarkable sun-dial with thirteen faces, dating from 1720.

It was usual to place on sun-dials appropriate mottoes expressing a sentiment exciting inspiration or giving a warning to better living. A dial that used to be at Paul's Cross, London, bore an inscription in Latin, which translated means, "I count none but the sunny hours." In an old sweet-scented garden in Sussex was a sun-dial with a plate bearing four mottoes, each for its own season: "After darkness, light;" "Alas, how swift;" "I wait whilst I move;" "So passes life." Sometimes short familiar proverbs were used like: "All things do wax and wane;" "The longest day must end;" "Make hay while the sun shines."

It is told of Lord Bacon, that, without intending to do so, he furnished the motto borne by a dial that stood in the old Temple Gardens in London. A young student was sent to him for a suggestion for the motto of the dial, then being built. His lordship was busy at work in his rooms when the messenger humbly and respectfully made his request. There was no answer. A second request met with equally oppressive silence and seeming ignorance of even the existence of the speaker. At last, when the petitioner ventured a third attack on the attention of the venerable chancellor, Bacon looked up and said sharply: "Sirrah, be gone about your business." "A thousand thanks, my lord," was the unexpected reply, "The very thing for the dial! Nothing could be better."

We see that the principle of the sun-dial has been recognized and utilized for many centuries; indeed, we still find sun-dials placed in gardens and parks although we rarely take the trouble to look to them for the time. Like the dinosaur and the saber-toothed tiger, they have had their day. They have been forced to give way to devices that overcame some of their objections; therefore we must not linger too long upon what is, after all, a closed chapter in the history of time-recording.

CHAPTER FOUR

Telling Time by the Water-Thief

Now we must take another backward step of thousands of years. In considering the subject of time-recording, it seems necessary to wear a pair of mental seven-league boots, for we must often pass back and forth over great periods at single strides. While men were still improving the sun-dial, its disadvantages were already recognized and search was being made for some other means of telling time.

Suppose, for example, that one had only a sun-dial about the house; how would one be able to tell time after sunset or on a dark day? How would one know the hour if he were surrounded by tall buildings or a thick growth of trees? And it might be very necessary to tell time under any of these conditions.

Then, again, merely as a question of accuracy, the sun-dial was not always reliable. It would get badly out of the way if used by travelers, since different markings were needed for different latitudes. While on shipboard the motion of the waves would cause the shadow to swing around in the most bewildering manner. Even under ideal conditions it was never absolutely exact, because the apparent motion of our steady-gaited old sun is not quite as dependable as most of us imagine.

Astronomers find that they must allow for what they call "equation of time" in order to make their calculations come out true. The question need not be discussed at this point, but it can be seen that, as humanity left its earliest care-free days and began to get busy, and hurried and anxious over its affairs, it came to feel that after all the sun-dial was not altogether sufficient for its needs.

For this reason we are now taking a third big backward step, returning, this time, not to the caveman but to ancient Babylon and Egypt, probably not less than twenty-seven hundred years ago and possibly much longer. In this way we meet the clepsydra.

The clepsydra was an interesting instrument, and it had an interesting name, which meant the "thief of water" and came from two Greek words meaning "thief" and "water"; you can trace this in our words "kleptomaniac" and "hydrant." We shall now examine a timepiece that was much more nearly a machine than was the simple shade-casting sun-dial.

The original idea was simple enough. At first, it was merely that of a vessel of water, having a small hole in the bottom, so that the liquid dripped out drop by drop. As the level within the jar was lowered, it showed the time upon a scale. Thus, if the hole were so small and the vessel were so large that it would require twenty-four hours for the water to drip away at an absolutely steady rate, it may be seen that the side of the vessel might easily have been marked with twenty-four divisions to indicate the hours. It may also be seen that the water would drip as rapidly at night or in shadow as in sunlight. And the clepsydra could be used indoors, which the sun-dial could not, although it required attention in that it must be regularly refilled and the orifice must always be kept completely open, because the slightest stoppage would retard the rate of dripping and the "clock" would run slow.

The sun, which, with the other heavenly bodies, had therefore been the sole reliance of the human race in its time-reckoning could now be ignored and the would-be timekeeper called to his aid another mighty servant from the forces of nature – that of gravitation.

The most interesting human fact, however, about the clepsydra is that it involved an entirely different conception of the marking of time. Now it was not so much a question of when as of how long. A good sun-dial set in a proper position would always indicate three o'clock when it was three o'clock, but the clepsydra might do no such thing. It would merely show how many hours had elapsed since last it was filled, and the steady drip, drip, drip of the escaping water could – and did – lower the surface quite as evenly at one time of day as at another.

We have already seen that the first purpose in marking time was merely for making appointments, but the clepsydra shows that, with its invention, mankind had already made some progress toward a new point of view. One important factor in this change was the very practical need of telling time at night, in stormy weather, or indoors, where the sun-dial could not be used. The clepsydra, on the other hand, worked equally well at any hour or place, and in all sorts of weather.

Nevertheless, it, too, proved to have certain faults. After a time, people noticed the interesting fact that water ran faster from a full vessel than from one which was nearly empty; this was, of course, because of the greater pressure. Since such a variation interfered with calculations, they hit upon the idea of a double vessel; the larger one below containing a float which rose as the vessel filled, thus marking the hours upon the scale, and the smaller one above, the one from which the water dripped, being kept constantly filled to the point of overflow.

This improved form of clepsydra opened a field of fascinating possibilities in time-recording —it gave the chance to make use of a machine. There is, perhaps, no more interesting point in studying human development than to see the steady, inevitable way in which mankind from its cave-dwelling days has tended toward machinery. Roughly, this progress may be characterized as of three stages.

First. Primitive man – an upright-standing animal, naked, unarmed, weak as compared with some creatures, slow as compared with others, clumsy as compared with still others – a creature with many physical disadvantages, but with the best brain in the animal kingdom.

Second. The tool-using man, who had begun to grasp weapons and to fashion implements, thus supplementing his natural abilities by artificial means.

Third. The machine-making man, who has fashioned to himself a mechanical "body" of incredible powers – that is to say, he has learned to intensify his own powers through artificial means which he has invented, as when he made the telescope to give himself greater vision; he has made inventions by means of which he can outrun the antelopes, outfly the birds, outswim the fishes, outgaze the eagles, and overmatch the elephants in sheer physical force – he can turn night into day, can send his voice across the continent, can strike crushing blows at a distance of many miles and can carry the movements of the stars in his pocket. Some phases of this third stage were foreshadowed when man first applied wheels and pulleys to his clepsydra.

Here, then, was water steadily raised or lowered by means of uniform dropping; here was a float whose motion was controlled by that of the water; here, in fact, was water-power with a means for applying it. Attach a cord to the float, cause it to turn a wheel by use of the pulley-principle, and the motion of the wheel would indicate the time. Still better, rig up a turning-pointer, increase its speed through the use of toothed gear-wheels, place it in front of a stationary disk divided to indicate the hours, and now the apparatus looked not unlike a modern clock. Or attach a bell and let it be caused to ring at a certain point in the motion – what was that but an alarm-clock? Ctesibus of Alexandra was the one who is believed first to have applied the toothed wheels to the clepsydra and this was about 140 B. C.

Clepsydrae were expensive of course; accurate mechanical work was never cheap until modern times. Cunning craftsmen spent their time upon costly decorations, and these water-clocks became triumphs of the jeweler's art, a gift for kings. Therefore, like the sun-dial, they drifted into Rome – that vast maelstrom of the ancient world. Imagine a great walled city of low flat-roofed buildings, with fronts and porches of great columns, a town mostly of stone and much of it of marble, gleaming white under the bright Italian sun, the streets thronged with men in tunics and togas and here and there some person of importance driving by, standing erect in his chariot drawn by four horses harnessed abreast. And statues everywhere, in the streets and about the buildings and in cool courtyards and gardens among green leaves. The ancients thought of sculpture as an outdoor thing, and where we have one statue in the streets or public places of our cities, they had a hundred. We treasure the remains of them as artistic wonders in our museums, but they put them indoors and out as common ornaments, and lived among them.

Presently we hear of the clepsydra being used in Roman law courts by command of Pompey, to limit the time of speakers. "This," says one writer of the day, "was to prevent babblings, that such as spoke ought to be brief in their speeches." It is not difficult to picture some pompous and tiresome togaed advocate, rolling out sonorous Latin syllables as he cites precedents and builds up arguments, while an unseen dropping checks the time against him, and to hear his indignant surprise – and the chuckles of his auditors – when the relentless water-clock cuts him short in the middle of some period. Martial, the Latin poet, referring to a tiresome speaker who repeatedly moistened his throat from a glass of water during the lengthy speech, suggested that it would be an equal relief to him and to his audience, if he were to drink from the clepsydra. But Roman lawyers were not guileless, and sometimes, so we are told, they tampered with the mechanical regulation or else introduced muddy water, which would run out more slowly.

This suggests one of the difficulties of the clepsydra. Still more serious was the fact that it would freeze on frosty nights. There were no Pearys among the ancient Romans; polar exploration interested them not at all; but they did spread their conquests into regions of colder weather – as when Julius Caesar mentions using the clepsydra to regulate the length of the night-watches in Britain. His keen mind noted by this means that the summer nights in Britain were shorter than those at Rome, a fact now known to be due to difference of latitude.

As late as the ninth century, a clepsydra was regarded as a princely gift. It is said, that the good caliph, Harun-al-Raschid, beloved by all readers of the "Arabian Nights," sent one of great beauty to Charlemagne, the Emperor of the West. Its case was elaborate, and, at the stroke of each hour, small doors opened to give passage to cavaliers. After the twelfth hour these cavaliers retired into the case. The striking apparatus consisted of small balls which dropped into a resounding basin underneath.

The clepsydra appears to have been used throughout the Middle Ages in some European countries, and it lingered along in Italy and France down to the close of the fifteenth century. Some of these water-clocks were plain tin tubes; some were hollow cups, each with a tiny hole at the bottom, which were placed in water and gradually filled and sank in a definite space of time.

When the clepsydra was introduced from Egypt into Greece, and later into Rome, one was considered enough for each town and was set in the market-place or some public square. It was carefully guarded by a civic officer, who religiously filled it at stated times. The nobility of the town and the wealthy people sent their servants to find out the exact time, while the poorer inhabitants were informed occasionally by the sound of the horn which was blown by the attendant of the clepsydra to denote the hour of changing the guard. This was much in the spirit of the calls of the watchmen in old England, and later in our New England, who were, in a way, walking clocks that shouted "Eleven o'clock and all's well," or whatever might be the hour.

Allowing for the fact that the clepsydra was none too accurate at the best and that its reservoir must occasionally be refilled, it can be seen that this early form of timepiece, having played its part, was ready to step off the stage when a more practical successor should arrive.

With one of its earliest successors we are familiar.

CHAPTER FIVE

How Father Time Got His Hour-Glass

Every now and then one sees a picture of a lean old gentleman, with a long white beard, flowing robes, and an expression of most misleading benignity. In spite of his look of kindly good humor, he is none too popular with the human race and his methods are not always of the gentlest. In one hand he carries the familiar scythe, and, in the other, the even more familiar hour-glass. By this we may assume that he began to be pictured in this way while the hour-glass was still in common use.

The principle of the hour-glass is so similar to that of the clepsydra, and its first use was so early, that it is somewhat of a misnomer to speak of it as a successor. About the only justification that can be made is that the clepsydra has long disappeared, while the sand-glass – if not the hour-glass – is still sold in the stores for such familiar uses as timing the boiling of eggs, the length of telephone-conversations, and other short-time needs.

Nothing could be much simpler than the hour-glass, in which fine sand poured through a tiny hole from an upper into a lower compartment. It had none of the mechanical features of the later clepsydræ; it did not adjust itself to astronomical laws like the perfected sun-dials; it merely permitted a steady stream of fine sand to pass through an opening at a uniform rate of speed, until one of the funnel-shaped bowls had emptied itself – then waited with entire unconcern until some one stood it upon its head and caused the sand to run back again.

However, it possessed some very solid advantages of its own. It would not freeze; it would not spill over; it did not need refilling; it would run at a steady rate whether the reservoir were full or nearly empty; it could be made very cheaply, and there was nothing about it to wear out.