Part 74

~A PRIMITIVE TWELVE-HOUR CLOCK~

It is a 12-hour clock, consisting of four copper jars partially built in masonry forming a stair-like structure. Commencing at the top jar each one drops into the next downward until the water reaches the solid bottom jar. In this lowest one a float, “the bamboo stick,” is placed and indicates the height of the water, and thus in a rude way gives the time. It is said to be set morning and evening by dipping the water from jar 4 to jar 1, so it runs 12 hours of our time. What are the uses of jars 2 and 3, since the water simply enters them and drips out again? No information could be obtained, but I venture an explanation and hope the reader can do better, as we are all of a family and there is no jealousy. When the top jar is filled for a 12-hour run it would drip out too fast during the first six hours and too slow during the second six hours, on account of the varying “head” of water. Now, the spigot of jar 2 could be set so that it would gain water during the first six hours, and lose during the second six hours, and thus equalize a little by splitting the error of jar 1 in two parts. Similarly, these two errors of jar 2 could be again split by jar 3 making four small variations in lowest jar, instead of one large error in the flow of jar 1. This could be extended to a greater number of jars, another jar making eight smaller errors.

The best thing the young student could do at this point would be to grasp the remarkable fact that the clock is not an old machine, since is covers only the comparatively short period from 1364 to the present day. Compared with the period of man’s history and inventions it is of yesterday. Strictly speaking, as we use the word clock, its age from De Vick to the modern astronomical is only about 540 years. If we take the year 1660, we find that it represents the center of modern improvements in clocks, a few years before and after that date includes the pendulum, the anchor and dead beat escapements, the minute and second hands, the circular balance and the hair spring, along with minor improvements. Since the end of that period, which we may make 1700, no fundamental invention has been added to clocks and watches. This becomes impressive when we remember that the last 200 years have produced more inventions than all previous known history--but only minor improvements in clocks! The application of electricity for winding, driving, or regulating clocks is not fundamental, for the time-keeping is done by the master clock with its pendulum and wheels, just as by any grandfather’s clock 200 years old. This broad survey of time measuring does not permit us to go into minute mechanical details.

Drawing by James Arthur.

Modern clocks commence with De Vick’s of 1364, which is the first unquestioned clock consisting of toothed wheels and containing the fundamental features of our present clocks. References are often quoted back to about 1000 A.D., but the words translated “clocks” were used for bells and dials at that date; so we are forced to consider the De Vick clock as the first till more evidence is obtained. It has been pointed out, however, that this clock could hardly have been invented all at once; and therefore it is probable that many inventions leading up to it have been lost to history. That part of a clock which does the ticking is called the “escapement,” and the oldest form known is the “Verge.”]

~EARLIEST CLOCKS HAD NO DIALS OR HANDS~

Scattered references in old writings make it reasonably certain that from about 1000 A.D. to 1300 A.D. bells were struck by machines regulated with this verge escapement, thus showing that the striking part of a clock is older than the clock itself. It seems strange to us to say that many of the earlier clocks were strikers only, and had no dials or hands, just as if you turned the face of your clock to the wall and depended on the striking for the time.

Photo by James Arthur.

ENGLISH BLACKSMITH’S CLOCK.]

A good idea of the old church clocks may be obtained from the picture herewith. Tradition has followed it down as the “English Blacksmith’s Clock.” It has the very earliest application of the pendulum. The pendulum is less than 3 inches long and is hung on the verge, or pallet axle, and beats 222 per minute. This clock may be safely put at 250 years old, and contains nothing invented since that date. Wheels are cast brass and all teeth laboriously filed out by hand. Pinions are solid with the axles, or “staffs,” and also filed out by hand. It is put together, generally by mortise, tenon and cotter, but it has four original screws all made by hand with the file. How did he thread the holes for these screws? Probably made a tap by hand as he made the screws. But the most remarkable feature is the fact that no lathe was used in forming any part--all staffs, pinions and pivots being filed by hand. This is simply extraordinary when it is pointed out that a little dead center lathe is the simplest machine in the world, and he could have made one in less than a day and saved himself weeks of hard labor. It is probable that he had great skill in hand work and that learning to use a lathe would have been a great and tedious effort for him. So we have a complete striking clock made by a man so poor that he had only his anvil, hammer and file. The weights are hung on cords as thick as an ordinary lead-pencil and pass over pulleys having spikes set around them to prevent the cords from slipping. The weights descend 7 feet in 12 hours, so they must be pulled up--not wound up--twice a day. The single hour hand is a work of art and is cut through like lace. Public clocks may still be seen in Europe with only one hand. Many have been puzzled by finding that old, rudely made clocks often have fine dials, but this is not remarkable when we state that art and engraving had reached a high level before the days of clocks.

Courtesy of Colgate and Company.

THE HANDS OF THE LARGEST CLOCK IN THE WORLD--ON THE ROOF OF THE COLGATE FACTORY.

This big clock faces the giant office buildings of down-town New York. Its dial is 38 feet in diameter and can be read easily at a distance of three miles, so that passengers on the incoming liners pick out the clock as one of their first sights of New York.

The next largest clock (on the Metropolitan Tower) is 26¹⁄₂ feet in diameter; the Westminster clock of London, 22¹⁄₂ feet.

The great clock weighs approximately 6 tons. The minute hand, 20 feet long, travels at its point 23 inches every minute; more than one-half mile each day.

The bed of this clock is 4 feet in length, the wheels and gears being made of bronze and pinions of hardened steel. The time train occupies about one-third of the bedplate, and has a main time wheel measuring 18¹⁄₃ inches in diameter. This train is equipped with Dennison’s double three-legged gravity escapement, which was invented by Sir Edmund Becket, chiefly for use on the famous Westminster clock, installed in the Parliament Buildings, in London, England. The use of this escapement is most advantageous for a gigantic clock of this kind as it allows the impulse given the pendulum rod to be always constant, and therefore does not permit any change of power or driving force of the clock to affect its time-keeping qualities.

It requires about 600 pounds of cast-iron to propel this time train, and the clock is arranged to run eight days without winding. The gravity arms of the escapement are fastened at a point very near the suspension spring, and the arms are fitted with bronze roller beat pins.

The dial contains 1134 square feet, or about one thirty-fifth of an acre. The numerals consist of heavy black strokes, 5 feet 6 inches long and 30 inches wide at the outer end, tapering to a point at the inner end. The circumference of the dial is approximately 120 feet. The distance from center to center of numerals is 10 feet, and the minute spaces are 2 feet.

The background on dial is painted white, and in the daytime the black numerals show up distinctly. At night the numerals, or hour marks, are designated by a row of incandescent bulbs placed in a trough 5 inches wide and 5 inches deep. The hands at night are outlined with incandescent electric lights, there being 27 lamps on the hour hand and 42 lamps on the minute hand.]

This picture shows the machinery necessary to operate a large modern tower clock.

The mechanism is held in place and confined entirely within a cast-iron structure which is firmly bolted to the floor. The wheels are composed of bronze, the pinions of steel (hardened) and the gears are machine cut. At the front of the clock is a small dial which enables one to tell exactly the position of the hands on the outside dials, and there is also a second hand to permit of very close regulation and adjustment.

Three ways are provided for the regulation. First by a knurled screw at the top of bed frame. Second by a revolving disc at the bottom of the pendulum ball. Very often by either of these two methods it is impossible to bring the clock to fractional seconds, and in order to permit of a nicety of adjustment there is a cup fitted at the top of the ball so that by inserting or taking out lead pellets, the rating can be brought to absolute time.

INDEPENDENCE HALL, PHILADELPHIA]

Where Does the Day Begin?

To understand this subject we must first appreciate that a day as we think of it is a division of time made by man for the purpose of his own reckoning. So far as the beginning of day is concerned, it begins at a different place in the world every hour; yes, every minute and every second in the day. As, however, the distance in feet where the day begins from one minute to another is so short that we can hardly notice it in such short measurements of time, we will look at the answer to the question from hour to hour. When you understand the subject from that point you can yourself see that the day actually begins at a different point of the earth every minute and every second of time.

How Much of the Earth Does the Sun Shine on at One Time?

The sun is shining on some part of the earth all the time and the shining of the sun makes the difference between day and night. Wherever the sun is shining it is day-time, and where the sun is not shining it is night-time.

To illustrate we will make use of an ordinary orange and a lighted gas jet. Let us take a long hat-pin and stick it through the orange from stem to stem. Now hold the orange by the ends of the hat-pin up before the lighted gas jet. You will notice that one-half of the orange is lighted, while the other half is dark. Of course, it is the half of the orange away from the light that is dark. Now, revolve the orange slowly on the hat-pin axis toward the light. When you have turned the orange half way round the part that was formerly dark is now lighted up and the other part is now dark.