Christopher And The Clockmakers Part 26

"I meant once to find out all about chronometers; but before I got started something interrupted me and I forgot it. I wasn't much interested in them anyhow, I'm afraid."

"And now you'd like a few points, eh?"

"Yes. I know I shall get a great deal better idea of them if you tell me," was the reply.

"If you weren't an American and I a Scotchman, I should say you were an Irishman," laughed his companion.

"Why?" demanded Christopher innocently.

"Because you sound as if you had kissed the Blarney Stone. Well, if you wish to learn about chronometers you have chosen a somewhat difficult subject. It leads pretty far, you see. However, I will do my best to give you at least a few facts about them. In the first place the earth actually revolves on its axis in twenty-three hours, fifty-six minutes, and four seconds. We commonly divide our day, however, into twenty-four hours and let it go at that. But astronomers reckon more accurately.

They call our day the solar day and instead of having a clock with twelve figures on it as we do, they use one with twenty-four."

Christopher glanced up with a smile.

"Why be so fussy about things like minutes and seconds?"

"Because sometimes such things as minutes and seconds make a great deal of difference. You may remember that when we were talking of sundials I told you they were not exact timekeepers."

"I do remember."

"You see, we reckon our day by two counts: one of them begins at noon and goes on--one, two, three, four o'clock, etc.--up to midnight; the other begins at midnight and ends at noon."

"That's simple enough. I get that all right."

"Now people didn't always do that. There were other countries that planned their day differently. The ancient Babylonians, for instance, began their day at sunrise; the Athenians and Jews at sunset; and the Egyptians and Romans at midnight."

"How funny! I thought that of course it had always been done as we do it," confessed Christopher, with frank astonishment.

"Not at all. Our present system of time-keeping has been evolved out of the past and, like many other such heirlooms, is the result of a vast amount of study. Centuries ago n.o.body knew how to reckon time or what to reckon it by. Some computed it by the sun and had what is known as the solar day--a span of twenty-four hours; others figured it by the moon and got a lunar day of twenty-four hours and fifty minutes; while still others resorted to the stars or constellations and reached a result known as sidereal time, a day of twenty-three hours, fifty-six minutes.

Now you see there is quite a bit of difference in these various reckonings. The difference might not matter so much on land, but when one is at sea and has to compute lat.i.tude and longitude, it matters a vast deal."

"Oh!" A light of understanding was slowly dawning on the boy.

"Now," went on McPhearson, "apparent solar time is dependent on the motion of the sun and is shown by the sundial; mean solar time, on the other hand, is shown by a correct clock; and the difference between the two--or the difference between apparent time and mean time is technically known as the equation of time, and is set forth in a nautical almanac published by the government."

McPhearson waited a moment.

"And that's what mariners use?"

"Yes."

"Then," hazarded Christopher after a moment's thought, "there really is exact time and common time."

"Broadly speaking, yes," acquiesced McPhearson. "Or in other words there is time scientifically measured and time that is measured by man-made laws. The difference, as I told you, is of more importance to astronomers and mariners than to anybody else; and yet the puzzle for many centuries balked those who sought to establish a perfect system of time-keeping. As better s.h.i.+ps were built and adventurous persons began to sail the ocean both for trade and conquest, captains soon discovered the stars and the compa.s.s could not be relied upon to furnish them the reliable information they needed in locating their position. Therefore, about 1713 England offered a prize of 20,000 to any one who should invent a timekeeper sufficiently accurate to enable navigators to ascertain from it longitude at sea."

The Scotchman paused to take from his table a box of tiny bra.s.s screws from which he selected one that was to his liking.

"Now there was living at this period John Harrison, a Yorks.h.i.+re clockmaker, who although quite a young man had made a clock with wooden works into which he had put a gridiron pendulum--a device he had thought out to overcome the difficulties resulting from atmospheric conditions.

This clock was so skillfully adjusted that it did not vary a second a month. So you can see that despite the fact Harrison was not a member of the Clockmakers' Company he was certainly qualified to be."

"And did he go after the prize money?"

"Apparently the offer tempted him. Perhaps he not only desired to win the fortune offered but also wished the fun of solving the riddle the government propounded. At any rate, in 1728 he came to London prepared to present drawings of an instrument he felt certain would turn the trick and had not his friends deterred him he would have placed these sketches before the commission. Fortunately, however, he had excellent advisers (among whom was honest John Graham) and they a.s.sured him he would stand a far better chance of securing a favorable hearing should he first construct the instrument of which he at present had nothing but pictures. Now such counsel as this was pretty disheartening to a young man who, fired with hope and ambition, had come all the way to London confidently expecting to have his plan hailed with joy when he arrived.

Nevertheless Harrison was open-minded enough to accept his friends'

guidance and acting upon it he went home again and worked for seven years on the instrument he had drawn out on paper."

"And then did he bring it to London?" was Christopher's breathless demand.

"Yes," affirmed McPhearson. "The contrivance, however, was by no means perfect. Still it showed sufficient promise to interest the commissioners and lead them to give Harrison permission to go to Lisbon on one of the king's s.h.i.+ps; that he might correct his reckonings by taking practical observations at sea. Moreover they also paid him 5,000 of the prize money to encourage him. This financial spur, together with the faith it represented, stimulated the patient instrument-maker to fas.h.i.+on a second timekeeper on which he spent four years of hard work.

But even this one, although better than the first, failed to meet the demands, and he tried again, taking ten years to perfect a third. This was smaller and as it seemed to foreshadow good results he was awarded the gold medal annually presented by the Royal Society for the most useful nautical discovery thus far made. Yet notwithstanding this triumph the article he had produced did not suit him. Experience had, in the meantime, taught him a great deal, and after more corrections and improvements he came again before the committee and asked that the device he now had might be given practical trial."

Christopher hitched his stool a little nearer.

"Now governments, like elephants and mastodons, move slowly, and by the time the coveted permission was granted poor Harrison was well-nigh seventy years old and instead of setting out on an ocean voyage for Jamaica he was forced to surrender his place to his son, William, whom he had trained up as one of his apprentices."

"Poor old duffer! I'll bet he was disappointed," came sympathetically from Christopher. "Think of his having to stay at home and miss the fun of seeing how his invention was working!"

"It was pretty tough," agreed McPhearson. "William, in the meantime, sailed out of Portsmouth harbor and after eighteen days of voyaging the vessel, supposed by ordinary calculation to be 13 50' west of that port, was by Harrison's watch 15 19', whereupon the captain of the s.h.i.+p immediately cried that it was worthless. If William had not been a chip of the old block and had inherited some of his father's courage, wisdom, and persistence, he would have lost his nerve at this crisis and allowed himself to come home beaten. But evidently he believed in the venture he had in hand. Perhaps, too, the thought of how disappointed his poor old dad would be were he to return spurred him to hold on with bulldog tenacity. So instead of being cowed by this apparent failure he insisted that if Madeira were correctly charted on the captain's map, it would be sighted the next day. So convincing was his prediction that the reluctant officer at length consented to continue on his course, and sure enough the following morning there loomed Madeira just as William had prophesied! Having won out on this forecast, William kept on predicting just where the other islands would be and behold, one after another they came into sight!"

"Hurray!" cried Christopher.

"Well, after a trip of sixty-one days the _Deptford_ reached Port Royal, and the chronometer (for that is what this new sort of watch really was) proved to be only about nine seconds slow. Then followed the voyage home. William Harrison had been gone five months in all--five months which to his poor, anxious old father must have seemed five years in length. During that entire time the chronometer had varied only one minute and five seconds."

"Pooh! That wasn't anything to get hot over," exploded Christopher.

"And yet a variation as great as that represented an error of eighteen miles--a big enough distance to admit of a s.h.i.+p being run on no end of rocks and shoals."

"I didn't realize it amounted to so many miles," was the sober reply.

"Probably the error even in miles did not shock people of that time as much as it would us, for they were accustomed to inaccuracies. Moreover such a record was worlds better than anything previously known. Yet notwithstanding this fact, the commissioners haggled over awarding the prize money and after advancing another 5,000 insisted that William make a second trip."

"Shucks!"

McPhearson paid no heed to the interruption.

"This time," continued he, "the undaunted young clockmaker embarked on an English man-of-war, the _Tartar_, and sailed for the Barbados, the chronometer gaining only forty-three seconds; and then back he came on the _New Elizabeth_, making the round trip of one hundred fifty-six days with only a total gain of fifty-four seconds in his father's instrument."

"Bravo! And so old Harrison at last got his money," a.s.serted Christopher with a satisfied sigh.

"Not yet. You move too fast, sonny. Governments do not bestow fortunes at your pace. Not they! This time the commissioners paid over a third 5,000, joining with it the demand that the elder Harrison explain to a company of experts exactly how his invention worked. In our day a man would have protected himself with a patent before he surrendered the requested information but the universe of the eighteenth century was less sophisticated. Patiently Harrison told his inquisitors everything they wanted to know and in 1765 they declared themselves satisfied with the instrument in every detail."

"Well, I should think it was high time!" scoffed the boy.

The Scotchman smiled at his indignation.

"Oh, don't imagine yourself through with the story yet," said he, "for even now more conditions were enjoined. Before the balance of the prize money was paid, one of the experts was appointed to construct a chronometer like Harrison's for the purpose not only of finding out whether every claim he made for it was true, but also to a.s.sure the board that other persons beside this one old man could make such an instrument. The fulfillment of this final condition consumed three years."

"Oh, rats! I should have told them they could keep their money--the old grannies!" jeered his listener wrathfully.