James Watt Part 9

Papin preferred gunpowder as a safer source of power than steam, but that was before it had been automatically regulated by the "Governor."

The governor has always been the writer's favorite invention, probably because it was the first he fully understood. It is an application of the centrifugal principle adapted and mechanically improved. Two heavy revolving b.a.l.l.s swing round an upright rod. The faster the rod revolves the farther from it the b.a.l.l.s swing out. The slower it turns the closer the b.a.l.l.s fall toward it. By proper attachments the valve openings admitting steam are widened or narrowed accordingly. Thus the higher speed of the engine, the less steam admitted, the slower the speed the more steam admitted. Hence any uniform speed desired can be maintained: should the engine be called upon to perform greater service at one moment than another, as in the case of steel rolling mills, speed being checked when the piece of steel enters the rolls, immediately the valves widen, more steam rushes into the engine, and _vice versa_. Until the governor came regular motion was impossible--steam was an unruly steed.

Arago describes the steam-gauge thus:

It is a short gla.s.s tube with its lower end immersed in a cistern of mercury, which is placed within an iron box screwed to the boiler steam-pipe, or to some other part communicating freely with the steam, which, pressing on the surface of the mercury in the cistern, raises the mercury in the tube (which is open to the air at the upper end), and its alt.i.tude serves to show the elastic power of the steam over that of the atmosphere.

The indicator he thus describes:

The barometer being adapted only to ascertain the degree of exhaustion in the condenser where its variations were small, the vibrations of the mercury rendered it very difficult, if not impracticable, to ascertain the state of the exhaustion of the cylinder at the different periods of the stroke of the engine; it became therefore necessary to contrive an instrument for that purpose that should be less subject to vibration, and should show nearly the degree of exhaustion in the cylinder at all periods. The following instrument, called the Indicator, is found to answer the end sufficiently. A cylinder about an inch diameter, and six inches long, exceedingly truly bored, has a solid piston accurately fitted to it, so as to slide easy by the help of some oil; the stem of the piston is guided in the direction of the axis of the cylinder, so that it may not be subject to jam, or cause friction in any part of its motion. The bottom of this cylinder has a c.o.c.k and small pipe joined to it which, having a conical end, may be inserted in a hole drilled in the cylinder of the engine near one of the ends, so that, by opening the small c.o.c.k, a communication may be effected between the inside of the cylinder and the indicator.

The cylinder of the indicator is fastened upon a wooden or metal frame, more than twice its own length; one end of a spiral steel spring, like that of a spring steel-yard, is attached to the upper part of the frame, and the other end of the spring is attached to the upper end of the piston-rod of the indicator.

The spring is made of such a strength, that when the cylinder of the indicator is perfectly exhausted, the pressure of the atmosphere may force its piston down within an inch of its bottom. An index being fixed to the top of its piston-rod, the point where it stands, when quite exhausted, is marked from an observation of a barometer communicating with the same exhausted vessel, and the scale divided accordingly.

Improvements come in many ways, sometimes after much thought and after many experimental failures. Sometimes they flash upon clever inventors, but let us remember this is only after they have spent long years studying the problem. In the case of the steam engine, however, a quite important improvement came very curiously. Humphrey Potter was a lad employed to turn off and on the stop c.o.c.ks of a Newcomen engine, a monotonous task, for, at every stroke one had to be turned to let steam into the boiler and another for injecting the cold water to condense it, and this had to be done at the right instant or the engine could not move. How to relieve himself from the drudgery became the question. He wished time to play with the other boys whose merriment was often heard at no great distance, and this set him thinking. Humphrey saw that the beam in its movements might serve to open and shut these stop c.o.c.ks and he promptly began to attach cords to the c.o.c.ks and then tied them at the proper points to the beam, so that ascending it pulled one cord and descending the other. Thus came to us perhaps not the first automatic device, but no doubt the first of its kind that was ever seen there. The steam engine henceforth was self-attending, providing itself for its own supply of steam and for its condensation with perfect regularity. It had become in this feature automatic.

The cords of Potter gave place to vertical rods with small pegs which pressed upward or downward as desired. These have long since been replaced by other devices, but all are only simple modifications of a contrivance devised by the mere lad whose duty it was to turn the stop c.o.c.ks.

It would be interesting to know the kind of man this precocious boy inventor became, or whether he received suitable reward for his important improvement. We search in vain; no mention of him is to be found. Let us, however, do our best to repair the neglect and record that, in the history of the steam engine, Humphrey Potter must ever be honorably a.s.sociated with famous men as the only famous boy inventor.

In the development of the steam engine, we have one purely accidental discovery. In the early Newcomen engines, the head of the piston was covered by a sheet of water to fill the s.p.a.ces between the circular contour of the movable piston and the internal surface of the cylinder, for there were no cylinder-boring tools in those days, and surfaces of cylinders were most irregular. To the surprise of the engineer, the engine began one day working at greatly increased speed, when it was found that the piston-head had been pierced by accident and that the cold water had pa.s.sed in small drops into the cylinder and had condensed the steam, thus rapidly making a more perfect vacuum. From this accidental discovery came the improved plan of injecting a shower of cold water through the cylinder, the strokes of the engine being thus greatly increased.

The year 1783 was one of Watt's most fruitful years of the dozen which may be said to have teemed with his inventions. His celebrated discovery of the composition of water was published in this year. The attempts made to deprive him of the honor of making this discovery ended in complete failure. Sir Humphrey Davy, Henry, Arago, Liebig, and many others of the highest authority acknowledged and established Watt's claims.

The true greatness of the modest Watt was never more finely revealed than in his correspondence and papers published during the controversy.

Watt wrote Dr. Black, April 21st, that he had handed his paper to Dr.

Priestley to be read at the Royal Society. It contained the new idea of water, hitherto considered an element and now discovered to be a compound. Thus was announced one of the most wonderful discoveries found in the history of science. It was justly termed the beginning of a new era, the dawn of a new day in physical chemistry, indeed the real foundation for the new system of chemistry, and, according to Dr.

Young, "a discovery perhaps of greater importance than any single fact which human ingenuity has ascertained either before or since." What Newton had done for light Watt was held to have done for water.

Muirfield well says:

It is interesting in a high degree to remark that for him who had so fully subdued to the use of man the gigantic power of steam it was also reserved to unfold its compound natural and elemental principles, as if on this subject there were to be nothing which his researches did not touch, nothing which they touched that they did not adorn.

Arago says:

In his memoir of the month of April, Priestley added an important circ.u.mstance to those resulting from the experiments of his predecessors: he proved that the weight of the water which is deposited upon the sides of the vessel, at the instant of the detonation of the oxygen and hydrogen, is precisely the same as the weights of the two gases.

Watt, to whom Priestley communicated this important result, immediately perceived that proof was here afforded that water was not a simple body.

Writing to his ill.u.s.trious friend, he asks:

What are the products of your experiment? They are _water_, _light_ and _heat_. Are we not, thence, authorised to conclude that water is a compound of the two gases, oxygen and hydrogen, deprived of a portion of their latent or elementary heat; that oxygen is water deprived of its hydrogen, but still united to its latent heat and light? If light be only a modification of heat, or a simple circ.u.mstance of its manifestation, or a component part of hydrogen, oxygen gas will be water deprived of its hydrogen, but combined with latent heat.

This pa.s.sage, so clear, so precise, and logical, is taken from a letter of Watt's, dated April 26, 1783. The letter was communicated by Priestley to several of the scientific men in London, and was transmitted immediately afterward to Sir Joseph Banks, the President of the Royal Society, to be read at one of the meetings of that learned body.

Watt had for many years entertained the opinion that air was a modification of water. He writes Boulton, December 10, 1782:

You may remember that I have often said, that if water could be heated red-hot or something more, it would probably be converted into some kind of air, because steam would in that case have lost all its latent heat, and that it would have been turned solely into sensible heat, and probably a total change of the nature of the fluid would ensue.

A month after he hears of Priestley's experiments, he writes Dr. Black (April 21, 1783) that he "believes he has found out the cause of the conversion of water into air." A few days later, he writes to Dr.

Priestley:

In the deflagration of the inflammable and dephlogisticated airs, the airs unite with violence--become red-hot--and, on cooling, totally disappear. The only fixed matter which remains is _water_; and _water_, _light_, and _heat_, are all the products. Are we not then authorised to conclude that water is composed of dephlogisticated and inflammable air, or phlogiston, deprived of part of their latent heat; and that dephlogisticated, or pure air, is composed of water deprived of its phlogiston, and united to heat and light; and if light be only a modification of heat, or a component part of phlogiston, then pure air consists of water deprived of its phlogiston and of latent heat?

It appears from the letter to Dr. Black of April 21st, that Mr. Watt had, on that day, written his letter to Dr. Priestley, to be read by him to the Royal Society, but on the 26th he informs Mr. DeLuc, that having observed some inaccuracies of style in that letter, he had removed them, and would send the Doctor a corrected copy in a day or two, which he accordingly did on the 28th; the corrected letter (the same that was afterward embodied verbatim in the letter to Mr. DeLuc, printed in the Philosophical Transactions), being dated April 26th. In enclosing it, Mr. Watt adds, "As to myself, the more I consider what I have said, I am the more satisfied with it, as I find none of the facts repugnant."

Thus was announced for the first time one of the most wonderful discoveries recorded in the history of science, startling in its novelty and yet so simple.

Watt had divined the import of Priestley's experiment, for he had mastered all knowledge bearing upon the question, but even when this was communicated to Priestley, he could not accept it, and, after making new experiments, he writes Watt, April 29, 1783, "Behold with surprise and indignation the figure of an apparatus that has utterly ruined your beautiful hypothesis," giving a rough sketch with his pen of the apparatus employed. Mark the prompt.i.tude of the master who had deciphered the message which the experimenter himself could not translate. He immediately writes in reply May 2, 1783:

I deny that your experiment ruins my hypothesis. It is not founded on so brittle a basis as an earthen retort, nor on _its_ converting water into air. I founded it on the other facts, and was obliged to stretch it a good deal before it would fit this experiment.... I maintain my hypothesis until it shall be shown that the water formed after the explosion of the pure and inflammable airs, has some other origin.

He also writes to Mr. DeLuc on May 18th:

I do not see Dr. Priestley's experiment in the same light that he does. It does not disprove my theory.... My a.s.sertion was simply, that air (_i.e._, dephlogisticated air, or oxygen, which was also commonly called vital air, pure air, or simple _air_) was water deprived of its phlogiston, and united to heat, which I grounded on the decomposition of air by inflammation with inflammable air, the residuum, or product of which, is only water and heat.

Having, by experiments of his own, fully satisfied himself of the correctness of his theory, in November he prepared a full statement for the Royal Society, having asked the society to withhold his first paper until he could prove it for himself by experiment. He never doubted its correctness, but some members of the society advised that it had better be supported by facts.

When the discovery was so daring that Priestley, who made the experiments, could not believe it and had to be convinced by Watt of its correctness, there seems little room left for other claimants, nor for doubt as to whom is due the credit of the revelation.

Watt encountered the difficulties of different weights and measures in his studies of foreign writers upon chemistry, a serious inconvenience which still remains with us.

He wrote Mr. Kirwan, November, 1783:

I had a great deal of trouble in reducing the weights and measures to speak the same language; and many of the German experiments become still more difficult from their using different weights and different divisions of them in different parts of that empire. It is therefore a very desirable thing to have these difficulties removed, and to get all philosophers to use pounds divided in the same manner, and I flatter myself that may be accomplished if you, Dr. Priestley, and a few of the French experimenters will agree to it; for the utility is so evident, that every thinking person must immediately be convinced of it.

Here follows his plan: Let the

Philosophical pound consist of 10 ounces, or 10,000 grains.

the ounce " " 10 drachms or 1,000 "

the drachm " " 100 grains.

Let all elastic fluids be measured by the ounce measure of water, by which the valuation of different cubic inches will be avoided, and the common decimal tables of specific gravities will immediately give the weights of those elastic fluids.

If all philosophers cannot agree on one pound or one grain, let every one take his own pound or his own grain; it will affect nothing but doses of medicines, which must be corrected as is now done; but as it would be much better that the identical pound was used by all. I would propose that the Amsterdam or Paris pound be a.s.sumed as the standard, being now the most universal in Europe: it is to our avoirdupois pound as 109 is to 100. Our avoirdupois pound contains 7,000 of our grains, and the Paris pound 7,630 of our grains, but it contains 9,376 Paris grains, so that the division into 10,000 would very little affect the Paris grain. I prefer dividing the pound afresh to beginning with the Paris grain, because I believe the pound is very general, but the grain local.

Dr. Priestley has agreed to this proposal, and has referred it to you to fix upon the pound if you otherwise approve of it. I shall be happy to have your opinion of it as soon as convenient, and to concert with you the means of making it universal.... I have some hopes that the foot may be fixed by the pendulum and a measure of water, and a pound derived from that; but in the interim let us at least a.s.sume a proper division, which from the nature of it must be intelligible as long as decimal arithmetic is used.

He afterward wrote, in a letter to Magellan:

As to the precise foot or pound, I do not look upon it to be very material, in chemistry at least. Either the common English foot may be adopted according to your proposal, which has the advantage that a cubic foot is exactly 1,000 ounces, consequently the present foot and ounce would be retained; or a pendulum which vibrates 100 times a minute may be adopted for the standard, which would make the foot 14.2 of our present inches, and the cubic foot would be very exactly a bushel, and would weigh 101 of the present pounds, so that the present pound would not be much altered. But I think that by this scheme the foot would be too large, and that the inconvenience of changing all the foot measures and things depending on them, would be much greater than changing all the pounds, bushels, gallons, etc. I therefore give the preference to those plans which retain the foot and ounce.

The war of the standards still rages--metric, or decimal, or no change.

What each nation has is good enough for it in the opinion of many of its people. Some day an international commission will doubtless a.s.semble to bring order out of chaos. As far as the English-speaking race is concerned, it seems that a decided improvement could readily be affected with very trifling, indeed scarcely perceptible, changes.

Especially is this so with money values. Britain could merge her system with those of Canada and America, by simply making her "pound" the exact value of the American five dollars, it being now only ten pence less; her silver coinage one and two s.h.i.+llings equal to quarter- and half-dollars, the present coin to be recoined upon presentation, but meanwhile to pa.s.s current. Weights and measures are more difficult to a.s.similate. Science being world-wide, and knowing no divisions, should use uniform terms. Alas! at the distance of nearly a century and a half we seem no nearer the prospect of a system of universal weights and measures than in Watt's day, but Watt's idea is not to be lost sight of for all that. He was a seer who often saw what was to come.

We have referred to the absence of holidays in Watt's strenuous life, but Birmingham was remarkable for a number of choice spirits who formed the celebrated Lunar Society, whose members were all devoted to the pursuit of knowledge and mutually agreeable to one another. Besides Watt and Boulton, there were Dr. Priestley, discoverer of oxygen gas, Dr.

Darwin, Dr. Withering, Mr. Keir, Mr. Galton, Mr. Wedgwood of Wedgwood ware fame, who had monthly dinners at their respective houses--hence the "Lunar" Society. Dr. Priestley, discoverer of oxygen, who arrived in Birmingham in 1780, has repeatedly mentioned the great pleasure he had in having Watt for a neighbor. He says:

I consider my settlement at Birmingham as the happiest event in my life; being highly favourable to every object I had in view, philosophical or theological. In the former respect I had the convenience of good workmen of every kind, and the society of persons eminent for their knowledge of chemistry; particularly Mr. Watt, Mr. Keir, and Dr. Withering. These, with Mr. Boulton and Dr. Darwin, who soon left us by removing from Lichfield to Derby, Mr. Galton, and afterwards Mr. Johnson of Kenilworth and myself, dined together every month, calling ourselves _the Lunar Society_, because the time of our meeting was near the full-moon--in order,

as he elsewhere says,