Men of Invention and Industry Part 6

But his most important invention, at this early period of his life, was his compensation pendulum. Every one knows that metals expand with heat and contract by cold. The pendulum of the clock therefore expanded in summer and contracted in winter, thereby interfering with the regular going of the clock. Huygens had by his cylindrical checks removed the great irregularity arising from the unequal lengths of the oscillations; but the pendulum was affected by the tossing of a ship at sea, and was also subject to a variation in weight, depending on the parallel of lat.i.tude. Graham, the well-known clock-maker, invented the mercurial compensation pendulum, consisting of a gla.s.s or iron jar filled with quicksilver and fixed to the end of the pendulum rod. When the rod was lengthened by heat, the quicksilver and the jar which contained it were simultaneously expanded and elevated, and the centre of oscillation was thus continued at the same distance from the point of suspension.

But the difficulty, to a certain extent, remained unconquered until Harrison took the matter in hand. He observed that all rods of metal do not alter their lengths equally by heat, or, on the contrary, become shorter by cold, but some more sensibly than others. After innumerable experiments Harrison at length composed a frame somewhat resembling a gridiron, in which the alternate bars were of steel and of bra.s.s, and so arranged that those which expanded the most were counteracted by those which expanded the least. By this means the pendulum contained the power of equalising its own action, and the centre of oscillation continued at the same absolute distance from the point of suspension through all the variations of heat and cold during the year.[5]

Thus by the year 1726, when he was only thirty-three years old, Harrison had furnished himself with two compensation clocks, in which all the irregularities to which these machines were subject, were either removed or so happily balanced, one metal against the other, that the two clocks kept time together in different parts of his house, without the variation of more than a single second in the month. One of them, indeed, which he kept by him for his own use, and constantly compared with a fixed star, did not vary so much as one whole minute during the ten years that he continued in the country after finishing the machine.[6]

Living, as he did, not far from the sea, Harrison next endeavoured to arrange his timekeeper for purposes of navigation.

He tried his clock in a vessel belonging to Barton-on-Humber; but his compensating pendulum could there be of comparatively little use; for it was liable to be tossed hither or thither by the sudden motions of the ship. He found it necessary, therefore, to mount a chronometer, or portable timekeeper, which might be taken from place to place, and subjected to the violent and irregular motion of a ship at sea, without affecting its rate of going. It was evident to him that the first mover must be changed from a weight and pendulum to a spring wound up and a compensating balance.

He now applied his genius in this direction. After pondering over the subject, he proceeded to London in 1728, and exhibited his drawings to Dr. Halley, then Astronomer-Royal. The Doctor referred him to Mr.

George Graham, the distinguished horologer, inventor of the dead-beat escapement and the mercurial pendulum. After examining the drawings and holding some converse with Harrison, Graham perceived him to be a man of uncommon merit, and gave him every encouragement. He recommended him, however, to make his machine before again applying to the Board of Longitude.

Harrison returned home to Barrow to complete his task, and many years elapsed before he again appeared in London to present his first chronometer.

The remarkable success which Harrison had achieved in his compensating pendulum could not but urge him on to further experiments. He was no doubt to a certain extent influenced by the reward of 20,000L. which the English Government had offered for an instrument that should enable the longitude to be more accurately determined by navigators at sea than was then possible; and it was with the object of obtaining pecuniary a.s.sistance to a.s.sist him in completing his chronometer that Harrison had, in 1728, made his first visit to London to exhibit his drawings.

The Act of Parliament offering this superb reward was pa.s.sed in 1714, fourteen years before, but no attempt had been made to claim it. It was right that England, then rapidly advancing to the first position as a commercial nation, should make every effort to render navigation less hazardous. Before correct chronometers were invented, or good lunar tables were prepared,[7] the ship, when fairly at sea, out of sight of land, and battling with the winds and tides, was in a measure lost. No method existed for accurately ascertaining the longitude. The ship might be out of its course for one or two hundred miles, for anything that the navigator knew; and only the wreck of his ship on some unknown coast told of the mistake that he had made in his reckoning.

It may here be mentioned that it was comparatively easy to determine the lat.i.tude of a ship at sea every day when the sun was visible. The lat.i.tude--that is, the distance of any spot from the equator and the pole--might be found by a simple observation with the s.e.xtant. The alt.i.tude of the sun at noon is found, and by a short calculation the position of the ship can be ascertained.

The s.e.xtant, which is the instrument universally used at sea, was gradually evolved from similar instruments used from the earliest times. The object of this instrument has always been to find the angular distance between two bodies--that is to say, the angle contained by two straight lines, drawn from those bodies to meet in the observer's eye. The simplest instrument of this kind may be well represented by a pair of compa.s.ses. If the hinge is held to the eye, one leg pointed to the distant horizon, and the other leg pointed to the sun, the position of the two legs will show the angular distance of the sun from the horizon at the moment of observation.

Until the end of the seventeenth century, the instrument used was of this simple kind. It was generally a large quadrant, with one or two bars moving on a hinge,--to all intents and purposes a huge pair of compa.s.ses. The direction of the sight was fixed by the use of a slit and a pointer, much as in the ordinary rifle. This instrument was vastly improved by the use of a telescope, which not only allowed fainter objects to be seen, but especially enabled the sight to be accurately directed to the object observed.

The instruments of the pre-telescopic age reached their glory in the hands of Tycho Brahe. He used magnificent instruments of the simple "pair of compa.s.ses" kind--circles, quadrants, and s.e.xtants. These were for the most part ponderous fixed instruments of little or no use for the purposes of navigation. But Tycho Brahe's s.e.xtant proved the forerunner of the modern instrument. The general structure is the same; but the vast improvement of the modern s.e.xtant is due, firstly, to the use of the reflecting mirror, and, secondly, to the use of the telescope for accurate sighting. These improvements were due to many scientific men--to William Gascoigne, who first used the telescope, about 1640; to Robert Hooke, who, in 1660, proposed to apply it to the quadrant; to Sir Isaac Newton, who designed a reflecting quadrant;[8]

and to John Hadley, who introduced it. The modern s.e.xtant is merely a modification of Newton's or Badley's quadrant, and its present construction seems to be perfect.

It therefore became possible accurately to determine the position of a ship at sea as regarded its lat.i.tude. But it was quite different as regarded the longitude that is, the distance of any place from a given meridian, eastward or westward. In the case of longitude there is no fixed spot to which reference can be made. The rotation of the earth makes the existence of such a spot impossible. The question of longitude is purely a question of TIME. The circuit of the globe, east and west, is simply represented by twenty-four hours. Each place has its own time. It is very easy to determine the local time at any spot by observations made at that spot. But, as time is always changing, the knowledge of the local time gives no idea of the actual position; and still less of a moving object--say, of a ship at sea. But if, in any locality, we know the local time, and also the local time of some other locality at that moment--say, of the Observatory at Greenwich we can, by comparing the two local times, determine the difference of local times, or, what is the same thing, the difference of longitude between the two places. It was necessary therefore for the navigator to be in possession of a first-rate watch or chronometer, to enable him to determine accurately the position of his ship at sea, as respected the longitude.

Before the middle of the eighteenth century good watches were comparatively unknown. The navigator mainly relied, for his approximate longitude, upon his Dead Reckoning, without any observation of the heavenly bodies. He depended upon the accuracy of the course which he had steered by the compa.s.s, and the mensuration of the ship's velocity by an instrument called the Log, as well as by combining and rectifying all the allowances for drift, lee-way, and so on, according to the trim of the ship; but all of these were liable to much uncertainty, especially when the sea was in a boisterous condition.

There was another and independent course which might have been adopted--that is, by observation of the moon, which is constantly moving amongst the stars from west to east. But until the middle of the eighteenth century good lunar tables were as much unknown as good watches.

Hence a method of ascertaining the longitude, with the same degree of accuracy which is attainable in respect of lat.i.tude, had for ages been the grand desideratum for men "who go down to the sea in ships." Mr.

Macpherson, in his important work ent.i.tled 'The Annals of Commerce,'

observes, "Since the year 1714, when Parliament offered a reward of 20,000L. for the best method of ascertaining the longitude at sea, many schemes have been devised, but all to little or no purpose, as going generally upon wrong principles, till that heaven-taught artist Mr.

John Harrison arose;" and by him, as Mr. Macpherson goes on to say, the difficulty was conquered, having devoted to it "the a.s.siduous studies of a long life."

The preamble of the Act of Parliament in question runs as follows: "Whereas it is well known by all that are acquainted with the art of navigation that nothing is so much wanted and desired at sea as the discovery of the longitude, for the safety and quickness of voyages, the preservation of ships and the lives of men," and so on. The Act proceeds to const.i.tute certain persons commissioners for the discovery of the longitude, with power to receive and experiment upon proposals for that purpose, and to grant sums of money not exceeding 2000L. to aid in such experiments. It will be remembered from what has been above stated, that a reward of 10,000L. was to be given to the person who should contrive a method of determining the longitude within one degree of a great circle, or 60 geographical miles; 15,000L. within 40 geographical miles; and 20,000L. within 30 geographical miles.

It will, in these days, be scarcely believed that little more than a hundred and fifty years ago a prize of not less than ten thousand pounds should have been offered for a method of determining the longitude within sixty miles, and that double the amount should have been offered for a method of determining it within thirty miles! The amount of these rewards is sufficient proof of the fearful necessity for improvement which then existed in the methods of navigation. And yet, from the date of the pa.s.sing of the Act in 1714 until the year 1736, when Harrison finished his first timepiece, nothing had been done towards ascertaining the longitude more accurately, even within the wide limits specified by the Act of Parliament. Although several schemes had been projected, none of them had proved successful, and the offered rewards therefore still remained unclaimed.

To return to Harrison. After reaching his home at Barrow, after his visit to London in 1728, he began his experiments for the construction of a marine chronometer. The task was one of no small difficulty. It was necessary to provide against irregularities arising from the motion of a ship at sea, and to obviate the effect of alternations of temperature in the machine itself, as well as the oil with which it was lubricated. A thousand obstacles presented themselves, but they were not enough to deter Harrison from grappling with the work he had set himself to perform.

Every one knows the beautiful machinery of a timepiece, and the perfect tools required to produce such a machine. Some of these tools Harrison procured in London, but the greater number he provided for himself; and many entirely new adaptations were required for his chronometer. As wood could no longer be exclusively employed, as in his first clock, he had to teach himself to work accurately and minutely in bra.s.s and other metals. Having been unable to obtain any a.s.sistance from the Board of Longitude, he was under the necessity, while carrying forward his experiments, of maintaining himself by still working at his trade of a carpenter and joiner. This will account for the very long period that elapsed before he could bring his chronometer to such a state as that it might be tried with any approach to certainty in its operations.

Harrison, besides his intentness and earnestness, was a cheerful and hopeful man. He had a fine taste for music, and organised and led the choir of the village church, which attained a high degree of perfection. He invented a curious monochord, which was not less accurate than his clocks in the mensuration of time. His ear was distressed by the ringing of bells out of tune, and he set himself to remedy them. At the parish church of Hull, for instance, the bells were harsh and disagreeable, and by the authority of the vicar and churchwardens he was allowed to put them into a state of exact tune, so that they proved entirely melodious.

But the great work of his life was his marine chronometer. He found it necessary, in the first place, to alter the first mover of his clock to a spring wound up, so that the regularity of the motion might be derived from the vibrations of balances, instead of those of a pendulum as in a standing clock. Mr. Folkes, President of the Royal Society, when presenting the gold medal to Harrison in 1749, thus describes the arrangement of his new machine. The details were obtained from Harrison himself, who was present. He had made use of two balances situated in the same plane, but vibrating in contrary directions, so that the one of these being either way a.s.sisted by the tossing of the ship, the other might constantly be just so much impeded by it at the same time. As the equality of the times of the vibrations of the balance of a pocket-watch is in a great measure owing to the spiral spring that lies under it, so the same was here performed by the like elasticity of four cylindrical springs or worms, applied near the upper and lower extremities of the two balances above described.

Then came in the question of compensation. Harrison's experience with the compensation pendulum of his clock now proved of service to him.

He had proceeded to introduce a similar expedient in his proposed chronometer. As is well known to those who are acquainted with the nature of springs moved by balances, the stronger those springs are, the quicker the vibrations of the balances are performed, and vice versa; hence it follows that those springs, when braced by cold, or when relaxed by heat, must of necessity cause the timekeeper to go either faster or slower, unless some method could be found to remedy the inconvenience.

The method adopted by Harrison was his compensation balance, doubtless the backbone of his invention. His "thermometer kirb," he himself says, "is composed of two thin plates of bra.s.s and steel, riveted together in several places, which, by the greater expansion of bra.s.s than steel by heat and contraction by cold, becomes convex on the bra.s.s side in hot weather and convex on the steel side in cold weather; whence, one end being fixed, the other end obtains a motion corresponding with the changes of heat and cold, and the two pins at the end, between which the balance spring pa.s.ses, and which it alternately touches as the spring bends and unbends itself, will shorten or lengthen the spring, as the change of heat or cold would otherwise require to be done by hand in the manner used for regulating a common watch." Although the method has since been improved upon by Leroy, Arnold, and Earnshaw, it was the beginning of all that has since been done in the perfection of marine chronometers. Indeed, it is amazing to think of the number of clever, skilful, and industrious men who have been engaged for many hundred years in the production of that exquisite fabric--so useful to everybody, whether scientific or otherwise, on land or sea the modern watch.

It is unnecessary here to mention in detail the particulars of Harrison's invention. These were published by himself in his 'Principles of Mr. Harrison's Timekeeper.' It may, however, be mentioned that he invented a method by which the chronometer might be kept going without losing any portion of time. This was during the process of winding up, which was done once in a day. While the mainspring was being wound up, a secondary one preserved the motion of the wheels and kept the machine going.

After seven years' labour, during which Harrison encountered and overcame numerous difficulties, he at last completed his first marine chronometer. He placed it in a sort of moveable frame, somewhat resembling what the sailors call a 'compa.s.s jumble,' but much more artificially and curiously made and arranged. In this state the chronometer was tried from time to time in a large barge on the river Humber, in rough as well as in smooth weather, and it was found to go perfectly, without losing a moment of time.

Such was the condition of Harrison's chronometer when he arrived with it in London in 1735, in order to apply to the commissioners appointed for providing a public reward for the discovery of the longitude at sea. He first showed it to several members of the Royal Society, who cordially approved of it. Five of the most prominent members--Dr.

Bailey, Dr. Smith, Dr. Bradley, Mr. John Machin, and Mr. George Graham--furnished Harrison with a certificate, stating that the principles of his machine for measuring time promised a very great and sufficient degree of exactness. In consequence of this certificate, the machine, at the request of the inventor, and at the recommendation of the Lords of the Admiralty, was placed on board a man-of-war.

Sir Charles Wager, then first Lord of the Admiralty, wrote to the captain of the Centurion, stating that the instrument had been approved by mathematicians as the best that had been made for measuring time; and requesting his kind treatment of Mr. Harrison, who was to accompany it to Lisbon. Captain Proctor answered the First Lord from Spithead, dated May 17th, 1736, promising his attention to Harrison's comfort, but intimating his fear that he had attempted impossibilities. It is always so with a new thing. The first steam-engine, the first gaslight, the first locomotive, the first steamboat to America, the first electric telegraph, were all impossibilities!

This first chronometer behaved very well on the outward voyage in the Centurion. It was not affected by the roughest weather, or by the working of the ship through the rolling waves of the Bay of Biscay. It was brought back, with Harrison, in the Orford man-of-war, when its great utility was proved in a remarkable manner, although, from the voyage being nearly on a meridian, the risk of losing the longitude was comparatively small. Yet the following was the certificate of the captain of the ship, dated the 24th June, 1737: "When we made the land, the said land, according to my reckoning (and others), ought to have been the Start; but, before we knew what land it was, John Harrison declared to me and the rest of the ship's company that, according to his observations with his machine, it ought to be the Lizard--the which, indeed, it was found to be, his observation showing the ship to be more west than my reckoning, above one degree and twenty-six miles,"--that is, nearly ninety miles out of its course!

Six days later--that is, on the 30th June--the Board of Longitude met, when Harrison was present, and produced the chronometer with which he had made the voyage to Lisbon and back. The minute states: "Mr. John Harrison produced a new invented machine, in the nature of clockwork, whereby he proposes to keep time at sea with more exactness than by any other instrument or method hitherto contrived, in order to the discovery of the longitude at sea; and proposes to make another machine of smaller dimensions within the s.p.a.ce of two years, whereby he will endeavour to correct some defects which he hath found in that already prepared, so as to render the same more perfect; which machine, when completed, he is desirous of having tried in one of His Majesty's ships that shall be bound to the West Indies; but at the same time represented that he should not be able, by reason of his necessitous circ.u.mstances, to go on and finish his said machine without a.s.sistance, and requested that he may be furnished with the sum of 500L., to put him in a capacity to perform the same, and to make a perfect experiment thereof."

The result of the meeting was that 500L. was ordered to be paid to Harrison, one moiety as soon as convenient, and the other when he has produced a certificate from the captain of one of His Majesty's ships that he has put the machine on board into the captain's possession.

Mr. George Graham, who was consulted, urged that the Commissioners should grant Harrison at least 1000L., but they only awarded him half the sum, and at first only a moiety of the amount voted. At the recommendation of Lord Monson, who was present, Harrison accepted the 250L. as a help towards the heavy expenses which he had already incurred, and was again about to incur, in perfecting the invention.

He was instructed to make his new chronometer of less dimensions, as the one exhibited was c.u.mbersome and heavy, and occupied too much s.p.a.ce on board.

He accordingly proceeded to make his second chronometer. It occupied a s.p.a.ce of only about half the size of the first. He introduced several improvements. He lessened the number of the wheels, and thereby diminished friction. But the general arrangement remained the same.

This second machine was finished in 1739. It was more simple in its arrangement, and less c.u.mbrous in its dimensions. It answered even better than the first, and though it was not tried at sea its motions were sufficiently exact for finding the longitude within the nearest limits proposed by Act of Parliament.

Not satisfied with his two machines, Harrison proceeded to make a third. This was of an improved construction, and occupied still less s.p.a.ce, the whole of the machine and its apparatus standing upon an area of only four square feet. It was in such forwardness in January, 1741, that it was exhibited before the Royal Society, and twelve of the most prominent members signed a certificate of "its great and excellent use, as well for determining the longitude at sea as for correcting the charts of the coasts." The testimonial concluded: "We do recommend Mr. Harrison to the favour of the Commissioners appointed by Act of Parliament as a person highly deserving of such further encouragement and a.s.sistance as they shall judge proper and sufficient to finish his third machine." The Commissioners granted him a further sum of 500L.

Harrison was already reduced to necessitous circ.u.mstances by his continuous application to the improvement of the timekeepers. He had also got into debt, and required further a.s.sistance to enable him to proceed with their construction; but the Commissioners would only help him by driblets.

Although Harrison had promised that the third machine would be ready for trial on August 1, 1743, it was not finished for some years later.

In June, 1746, we find him again appearing before the Board, asking for further a.s.sistance. While proceeding with his work he found it necessary to add a new spring, "having spent much time and thought in tempering them." Another 500L. was voted to enable him to pay his debts, to maintain himself and family, and to complete his chronometer.

Three years later he exhibited his third machine to the Royal Society, and on the 30th of November, 1749, he was awarded the Gold Medal for the year. In presenting it, Mr. Folkes, the President, said to Mr.

Harrison, "I do here, by the authority and in the name of the Royal Society of London for the improving of natural knowledge, present you with this small but faithful token of their regard and esteem. I do, in their name congratulate you upon the successes you have already had, and I most sincerely wish that all your future trials may in every way prove answerable to these beginnings, and that the full accomplishment of your great undertaking may at last be crowned with all the reputation and advantage to yourself that your warmest wishes may suggest, and to which so many years so laudably and so diligently spent in the improvement of those talents which G.o.d Almighty has bestowed upon you, will so justly ent.i.tle your constant and unwearied perseverance."

Mr. Folkes, in his speech, spoke of Mr. Harrison as "one of the most modest persons he had ever known. In speaking," he continued, "of his own performances, he has a.s.sured me that, from the immense number of diligent and accurate experiments he has made, and from the severe tests to which he has in many ways put his instrument, he expects he shall be able with sufficient certainty, through all the greatest variety of seasons and the most irregular motions of the sea, to keep time constantly, without the variation of so much as three seconds in a week,--a degree of exactness that is astonishing and even stupendous, considering the immense number of difficulties, and those of very different sorts, which the author of these inventions must have had to encounter and struggle withal."

Although it is common enough now to make first-rate chronometers--sufficient to determine the longitude with almost perfect accuracy in every clime of the world--it was very different at that time, when Harrison was occupied with his laborious experiments.

Although he considered his third machine to be the ne plus ultra of scientific mechanism, he nevertheless proceeded to construct a fourth timepiece, in the form of a pocket watch about five inches in diameter.

He found the principles which he had adopted in his larger machines applied equally well in the smaller, and the performances of the last surpa.s.sed his utmost expectations. But in the meantime, as his third timekeeper was, in his opinion, sufficient to supply the requirements of the Board of Longitude as respected the highest reward offered, he applied to the Commissioners for leave to try that instrument on board a royal ship to some port in the West Indies, as directed by the statute of Queen Anne.

Though Harrison's third timekeeper was finished about the year 1758, it was not until March 12, 1761, that he received orders for his son William to proceed to Portsmouth, and go on board the Dorsetshire man-of-war, to proceed to Jamaica. But another tedious delay occurred.

The ship was ordered elsewhere, and William Harrison, after remaining five months at Portsmouth, returned to London. By this time, John Harrison had finished his fourth timepiece--the small one, in the form of a watch. At length William Harrison set sail with this timekeeper from Portsmouth for Jamaica, on November 18th, 1761, in the Deptford man-of-war. The Deptford had forty-three ships in convoy, and arrived at Jamaica on the 19th of January, 1762, three days before the Beaver, another of His Majesty's ships-of-war, which had sailed from Portsmouth ten days before the Deptford, but had lost her reckoning and been deceived in her longitude, having trusted entirely to the log.

Harrison's timepiece had corrected the log of the Deptford to the extent of three degrees of longitude, whilst several of the ships in the fleet lost as much as five degrees! This shows the haphazard way in which navigation was conducted previous to the invention of the marine chronometer.

When the Deptford arrived at Port Royal, Jamaica, the timekeeper was found to be only five and one tenth seconds in error; and during the voyage of four months, on its return to Portsmouth on March 26th, 1762, it was found (after allowing for the rate of gain or loss) to have erred only one minute fifty-four and a half seconds. In the lat.i.tude of Portsmouth this only amounted to eighteen geographical miles, whereas the Act had awarded that the prize should be given where the longitude was determined within the distance of thirty geographical miles. One would have thought that Harrison was now clearly ent.i.tled to his reward of 20,000L.

Not at all! The delays interposed by Government are long and tedious, and sometimes insufferable. Harrison had accomplished more than was needful to obtain the highest reward which the Board of Longitude had publicly offered. But they would not certify that he had won the prize. On the contrary, they started numerous objections, and continued for years to subject him to vexatious delays and disappointments. They pleaded that the previous determination of the longitude of Jamaica by astronomical observation was unsatisfactory; that there was no proof of the chronometer having maintained a uniform rate during the voyage; and on the 17th of August, 1762, they pa.s.sed a resolution, stating that they "were of opinion that the experiments made of the watch had not been sufficient to determine the longitude at sea."

It was accordingly necessary for Harrison to pet.i.tion Parliament on the subject. Three reigns had come and gone since the Act of Parliament offering the reward had been pa.s.sed. Anne had died; George I. and George II. had reigned and died; and now, in the reign of George III.--thirty-five years after Harrison had begun his labours, and after he had constructed four several marine chronometers, each of which was ent.i.tled to win the full prize,--an Act of Parliament was pa.s.sed enabling the inventor to obtain the sum of 5000L. as part of the reward. But the Commissioners still hesitated. They differed about the tempering of the springs. They must have another trial of the timekeeper, or anything with which to put off a settlement of the claim. Harrison was ready for any further number of trials; and in the meantime the Commissioners merely paid him a further sum on account.