Gradually the excitement concerning the diamond robbery died away as do ripples in a pool and once more Christopher found himself settling down on the little wooden stool at McPhearson's elbow. The two had by this time become great friends, the boy preferring the companionship of the little Scotchman to that of any one else in the store. Perhaps this preference grew in a measure out of the fact that McPhearson appeared to like him and make more effort to entertain him than did the other clerks; perhaps also he had discovered that the clockmaker, when he did speak, was better worth listening to.

Be that as it may, he sallied into the repair department very glad to be there again.

"I feel as if I hadn't had a clock lesson for ages," observed he, as he sat down.

"Clock lesson? What do you mean?" The man with the swift-moving hands shot him a quick, puzzled glance.

"Oh, don't think I am here to steal your trade," retorted Christopher mischievously. "I only mean that so far as I am concerned the clock world stopped with Quare, Tompion, and Graham."

"Indeed it didn't," contradicted the Scotchman, instantly bristling. "Though if it had, you would not need to be pitied for those makers would have bequeathed you some pretty fine products. And when you consider that Tompion, at least, began life as a blacksmith it is the more remarkable. Think what it meant to work out of such a crude, rough trade into one so delicate! Still, it was an age of marvels—a strange, fantastic, interesting era in which to have lived. Many members of the Clockmakers' Company were blacksmiths who had graduated into this higher calling and now boasted their own shops and apprentices. These latter men helped about under supervision, learning the trade and completing from eight to ten years of service before being taken in turn into the guild and permitted to make clocks. In the meantime they prepared simple parts of the work and made themselves useful in any direction they were able, even running errands or standing at the shop door and coaxing the passers-by to come in and purchase."

"Pretty primitive advertising," smiled Christopher.

"Advertising was primitive in those days," agreed McPhearson. "Sometimes when trade was dull the unfortunate apprentices were sent out to tour the streets and bring in customers. Or the present of a watch or clock would be made to the king or some nobleman of wealth and influence in the hope that such a gift would stimulate others to buy. No doubt even the celebrated Graham, in the days of his apprenticeship to Tompion, may have had some of these humble duties to perform. But if so they failed to dash his enthusiasm for his profession, for you see how well he profited by his teaching and what a master at clockmaking he finally became. He had always been an ingenious fellow interested in evolving mathematical instruments of all sorts."

"Were his clocks as good as Tompion's?" queried Christopher.

"As to that, the two were pretty well matched," was the answer. "Graham, however, concentrated most of his skill on watches while Tompion put the major part of his talent into long-case clocks which were unrivaled. For, by this time, with the gradual development and improvement of clock machinery, it was possible to make grandfather, or long-case, clocks that kept excellent time. The defects of the old wheel escapement of the thirteenth, fourteenth, and fifteenth centuries were, as I told you, remedied in part by the invention of the fusee, a device for equalizing the movement. Then came the conversion of such clocks into pendulum clocks—no very difficult matter. One of the balls on the verge was removed, thereby making the verge longer and increasing the weight of the other ball. Then such clocks, together with those having a crown wheel escapement, went in turn out of vogue and the anchor escapement ushered in what is commonly known as the grandfather clock. It was in producing this particular type of timepiece that Tompion and Graham excelled. The pendulum was hung from a thin steel spring instead of being placed on an axis carrying pallets and could swing without friction."

"And whose scheme was that?"

"It is generally conceded that a Dutchman by the name of Fromanteel brought the modern pendulum idea into England. You will recall that early in clock history there were some pendulums of a very unsatisfactory nature in use—pendulums that were regulated by weights and dangled at the back or across the front of old brass clocks."

"I remember, yes."

"Well, it was that same pendulum principle carried to greater perfection and now scientifically applied which made the present grandfather, or long-case, clock possible. Certainly Fromanteel did a vast service to English clockmaking when he brought this solution of the pendulum problem to London, for with the anchor, or dead-beat escapement, combined with a long pendulum terminating in a heavy bob, the force of gravity caused such slight variation that the motion was practically harmonic and had only a very minor effect on the clock. For a long case, you see, has an exceedingly confined arc of oscillation because the swing of the pendulum is so limited. It is this length of pendulum together with its almost harmonic motion which results in the excellent time-keeping done by clocks of the "grandfather" class. The time a pendulum takes to vibrate always depends on its length—that is, the distance between the center of suspension and the center of gravity of the bob."

McPhearson paused to hold to the light a small brass pivot he was filing.

"Just here," continued he, "we stumble upon still another of the multiple tribulations of the clockmaker. If a big clock is expected to do any very fine work the latitude of the place in which it is to be put must be taken into consideration. For example, experiment has proved that the length of a pendulum vibrating seconds at London will not serve as accurately in other latitudes, because according to the laws of gravity the length of seconds increases in a specific ratio as we advance from the equator toward the poles. The clockmaker must, therefore, take care to regulate the length of his pendulum to correspond with this law."

"Great Scott! Why, I never dreamed there was so much to clockmaking!" gasped the astonished Christopher.

"Oh, the making of a finely adjusted, close-running clock is far more of a science than a trade, laddie. It isn't just making a lot of wheels that will turn, hands that will point, or a mechanism that will tick—wonderful as all that is," asserted McPhearson.

"I don't believe most persons realize it isn't."

"Those who dip below the surface and are better informed know the truth; as for the others—we must not expect too much of a hurrying world, son. Any branch of knowledge takes us very far if we follow it to the end. Why, look at me! I have spent all my life with clocks and what do I know about them?"

"A great deal," was the prompt retort.

"Very little, my boy; very little indeed!" sighed the old man. "I couldn't make one. Nevertheless I have had great pleasure in hunting down what I have learned. It is an interesting subject and one that never seems to exhaust itself. For all the wonders of my trade are not yet told. When, for instance, they put the clock on the Metropolitan Life Insurance building here in New York an undreamed-of pinnacle in clock construction was reached. There was a time when the clock on the London Houses of Parliament was the last word in the art—a veritable triumph of the horologe. Not only was it the largest timepiece in the world, but it seemed then the most miraculous."

"What date was that?"

"Back in 1860. Even I remember what a sensation this masterpiece created. It was designed by E. B. Dennison, afterward Lord Grimthorpe, and was placed one hundred and eighty feet above the ground—some halfway up the tower of one of the buildings. Now that fact in itself made the undertaking difficult, for the weather always has its effect on a clock, and to put one in such an exposed position created a problem at the outset. Moreover, perched up there in the sight of all London to serve as the chief timekeeper of the city, it could not be allowed to indulge in whims and caprices lest the populace be led astray by its inaccuracies and turn to cursing it. No, if it was to be there at all it must furnish correct information. Londoners could not afford to lose their trains, be late to their appointments, or miss their tea." The Scotchman uttered a soft laugh.

"Yes," continued he, as if the fancy pleased him, "when you are posted up in such a conspicuous spot as that, every one of your backslidings will be common property. And for that reason not only the reputation of the clock itself but that of its maker was at stake. Moreover, since the height at which the dial was to be set was so great, every part of the timepiece had to be of mammoth size."

"Of course it had," agreed Christopher. "I had almost forgotten that."

"A pretty gigantic project it was for a clockmaker, I can tell you," went on McPhearson. "Well, at last the clock was made and the scale of its dimensions sounded like a page from Gulliver's Travels. Each of the dials was of opalescent glass set in a framework of iron and was twenty-two feet or more in diameter. The figures that indicated the hours were two feet long and the minute spaces a foot square. Three sets of works were required to drive the various divisions of the mechanism: one moved the hands; another struck the hours; and still another rang the chimes. As for the pendulum—ah, here was a pendulum indeed! It was thirteen feet long and weighed seven hundred pounds."

"Jove!" murmured Christopher.

"Some pendulum, eh? What wouldn't the old clockmakers—Tompion, Quare, Fromanteel, Graham and the rest have given to see it! They probably never even imagined a clock of such proportions."

"Neither did I!" his companion announced. "How often did this giant have to be wound up?"

"The clock part was wound once a week; the striking part twice. And speaking of the striking part, you may like to know that the hour bell weighed thirteen tons and the four quarter-hour bells eight tons."

"Isn't it the biggest clock ever made?"

"It is probably one of the most powerful and most accurate of the large ones," nodded McPhearson, "although others are to be found with bigger dials. But it is no longer the largest clock in the world because since it was constructed several American rivals for that honor have arisen. One of them is right here in your own little old city of New York and the other is located on the New Jersey side of the Hudson River."

But Christopher's mind was still intent on the London masterpiece.

"How much do you suppose the English clock cost?" speculated he. "A fortune, I'll bet."

"I can tell you, for I happen to recall the figures," replied McPhearson. "Its price was $110,000."

"And cheap at that," grinned Christopher. "At least, I wouldn't undertake to produce it for that money."

"Nor I," echoed the Scotchman, returning the lad's smile. "I suppose when it was made nobody ever expected to see it equaled. And yet such strides are we making in science that here we are with a clock that is in many ways even more miraculous."

"You mean the one on the Metropolitan Life Insurance building?"

"The same," was the quick answer. "Surely you must grant that to be ahead of the one in London. It is interesting also to note how these two mammoth timepieces differ. The dial of our New York clock, instead of being of glass, is, as you know, of concrete faced with blue and white mosaic tiling. The figures indicating the hours are four feet high and the minute marks ten inches in diameter. The minute hands are twelve feet from center to tip and together weigh a thousand pounds; while the hour hands measure eight feet four inches from center to tip and weigh seven hundred pounds apiece."

"Mercy on us! I didn't realize it was such a whale of a thing!"

"A prophet is not without honour save in his own country," laughed the old clockmaker. "Here you sit almost under the shadow of one of the largest timepieces in the universe and fail to appreciate the wonder that towers above your head. Well, well! Perhaps you will treat your native land with more respect after this. Certainly you will regard this Metropolitan Life clock with greater awe and bless your stars that one of its hands hasn't blown down on top of you. Think of those gigantic pointing fingers being built on iron frames sheathed with copper and made to revolve on roller bearings!"

"I give you my word I shall think of it the next time I look up at them," responded Christopher. "How on earth can they make such a tremendous machine go?"

"It is controlled automatically from the director's room, where a master clock also controls a hundred others scattered throughout the building. This same mechanism controls in addition various electrical devices, such as signal bells, etc. It is all very wonderful. And the half is not told yet, for the tricks it performs at night are almost more amazing than are those it performs by day."

"I seldom see it in the evening," Christopher explained. "We are always starting out into the suburbs just when New York is beginning to wake up."

"New York can hardly be called asleep at any time," McPhearson chuckled, "so I must take your lamentation with a grain of salt. But it is rather of a pity you shouldn't have had the chance to see that clock after dark. Not that it isn't beautiful in the daylight. Its chimes certainly ring just as sweetly one time as another. Nevertheless I enjoy them best after the city gets a little bit quiet (which it seldom does until well toward morning). Those chimes, remember, are a replica of the set at Cambridge, England, and play a theme composed by Handel, the old composer."

"Why on earth didn't some one tell me all this before?"

"I'm sure I don't know, unless your dad was too busy or assumed you had read of the clock in the newspapers."

"It is never safe to assume I know anything," retorted Christopher naÏvely. "I know such a queer collection of stuff, you see. It's odd, isn't it, the truck that sticks in your memory? If I could only remember things that are worth while as easily as I often do things that aren't I should know quite a lot".

"That is the way with all of us, laddie," the old man on the work bench confessed. "I myself would gladly part with a vast deal I have acquired and never yet found a use for."

"We ought to have mental rummage sales and bundle out the rubbish we don't need," Christopher remarked.

The Scotchman hailed the suggestion with delight.

"That would be a capital scheme," acclaimed he. "The only trouble would be to find purchasers for our outgrown ideas."

"Oh, somebody would like them," put in Christopher cheerfully. "Mother says there are always people who will buy anything that is cheap no matter what it is."

"But my old ideas are not cheap ones," objected the clockmaker. "On the contrary, some of them cost me a great deal in the day of them; they are simply worn out and old-fashioned."

"They'd sell—never fear. Mother declares people buy the most impossible truck. A thing is seldom so bad that nobody wants it."

"Then that is certainly what we must do with our intellectual junk," was McPhearson's instant answer. "Suppose we advertise a sale of it? I will cheerfully part with 'The Boy Stood on the Burning Deck' which I committed to memory when I was eight years old. I'd sell it outright or would exchange it for one of Shakespeare's sonnets."

Christopher greeted the whimsey with a laugh.

"Now I," began he, "would sell or swap the water routes from most of our inland cities. We had to learn them when I studied geography and as I have never wanted to ship goods from St. Paul to Philadelphia, for example, I have found no use for them."

"You may some day."

"I'll risk it. If I did want them I could, perhaps, buy them back," flashed Christopher.

"What price would you set upon such possessions?"

"You mean the water routes? Well, it cost me a good deal of trouble to memorize them; still, I'd be glad to let them go cheap and be rid of them. I'd trade them for—let me see—an equal number of facts about wireless. With them I'd throw in all my—" he stopped suddenly.

"All your what?"

"I was going to say all my Latin but changed my mind," the boy replied. "I guess, everything considered, I'd better keep that. It might come in handy sometime. It did the other day."

"Oh, I'd keep your Latin, by all means," the Scotchman agreed.

A pause, weighted with humorous imaginings, fell between them until Christopher broke out:

"Mr. McPhearson!"

"Well?"

"How would you like to swap some more information about that clock on the Metropolitan Life building for my water routes?"

Gravely the clockmaker reflected.

"I'm afraid I haven't much more use for water routes just at present than you have," answered he. "I will, however, make a bargain with you. I will advance to you some more of what I know about that clock, if you will pledge yourself to let me have the water routes should I require them. Is that a bargain?"

"I'll sign up to that," came without hesitation from the lad. "In fact, after thinking it over, I guess it would be wiser for me not to agree to deliver the goods immediately. I'll have to hunt them up and—and—dust them first," concluded he with an impish grimace.

"I certainly should insist they be handed over in good condition," asserted McPhearson. "That would be only fair since what I give you in return is new and up to date. This clock on the insurance building is one of the most unique timepieces yet made. You cannot expect to receive information about it without offering something pretty valuable in exchange."

"No, indeed."

"That water route from St. Paul, for instance—I should never accept it if it began well and afterward became vague and uncertain; and should you break it off before you reached Philadelphia and excuse yourself by telling me that you had forgotten it—"

"You broke off about the clock, you know," interrupted Christopher.

"Yes. Nevertheless, I cannot be accused of having forgotten the information, and to prove it I will say that what I intended to add was that at night the numerals on the dial are not only illuminated but a flashlight from the tower sends out the time to those too far away either to see the face of the clock or hear it strike. A series of white flashes mark the hours, and the quarter hours are indicated by red flashes. Out over the land shoot these lights—out over the sea too. It is a mighty beacon—a great, throbbing, live thing that from its place high above the city keeps constant watch and slumbers not nor sleeps."

Christopher looked into the old man's eyes.

"I don't believe," ventured he, with a wistful expression, "it would be fair to swap any of the stuff I know for yours. You see, the things you have stored away in your mind are so much—so much finer."

"They weren't at first, laddie," returned McPhearson kindly. "I gathered a deal of worthless material before it occurred to me I could improve its quality. Then one day I said to myself, 'Why isn't it just as possible to collect beautiful and interesting thoughts as to collect stamps, or china teapots, or anything else?' So I set about weeding out the good from the unprofitable and found the scheme worked perfectly. If you don't believe it, try the plan yourself sometime, sonny."

"I'm going to," affirmed Christopher with earnest emphasis.

The Scotchman bent to file the tooth of a small brass wheel.

"Before we drop the subject of giant clocks," continued he presently, "I must warn you not to forget the monster newly set up by the Colgates on their building that skirts the Jersey shore of the Hudson. It is a veritable Titan with a dial fifty feet in diameter and hands measuring thirty-seven and a quarter feet and twenty-seven and a half feet in length. For miles down New York harbor it is visible, a formidable contestant for world supremacy."

"Clocks seem to grow bigger and bigger, don't they?" mused the boy.

"I hope they grow better and better—a far finer achievement, to my way of thinking," was the craftsman's answer.