406 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL 



[October 



which it traversed, and the external atmosphere forces it to descend. To 

 effect the necessary refrigeration, Papiii, as we know, was satisfied 

 with removing the pan of fuel which heated the l)ottoni of his metal 

 cylinder. Newromen and Cawley eni])loyed a process much better in 

 every respect , they caused a considerable quantity of cold water to flow 

 into the ring:-like space contained between the external surface of the 

 cylinder of their enfiine and a second cylinder, a little larger, in which it 

 was enclosed. Cold thus was communicated gradually to the whole 

 . thickness of (he metal, and ultimately reached the steam itself* 



Papin's machine, thus perfectedt as to the manner of refrigerating the 

 steam, or of cundensing it. excited the greatest interest in the mine pro- 

 prietors—it extended rapidly into several counties of England and ren- 

 dered important service ; the little energy of its movements, a necessary 

 consequence of the slo«Tiess with which the steam was refrigerated and 

 lost its ebisticity, was however a deep source of regret. Chance luckily 

 pointed out a very simple means of remedying this inconvenience. 



In the commcncemetit of the eighteenth century, the art of stuffing 

 large metal cylinders and closing them hermetically by means of metal 

 pistons was still in its infancy ; therefore, in the first engines of New- 

 comen the piston was covered with a layer of water for the purpose of 

 filling up the vacancies between the circular centre of this moveable 

 piece, and the surface of the cylinder. To the great surprise of its con- 

 structors, one of their engines seemed to oscillate much more rapidly 

 one day than it did generally. After examining it carefully, they saw 

 clearly that on that day the piston had a hole in it, and that the cold 

 water fell in driplets, which in passing through the steam were rapidly 

 dissipated. From this fortuitous observation is to be dated the com- 

 plete suppression of external refrigeration and the adoption of the rose 

 spout which carries a nlwirer of cold water through the whole extent of 

 the cylinder, at the time pointed out by the descent of the piston. The 

 action thus acquires the desired rapidity. 



Let us see also, if chance has not a share in another improvement 

 equally important. The first engine of Newcomen requires the closest 

 attendance on the part of the person, who was constantly employed in 

 opening, and shutting the cocks, either to introduce aqueous steam into 

 the cylinder, or to throw into it a jet of cold water for the purpose of 

 condensation. It happened one day that this pers'm was a youth named 

 Henry Potter, who was very anxious of joining in the joyous games of his 

 playfellows. He is burning with the desire of joining them, but the task 

 which is confided to him, does not allow half a minute's absence. His 

 head is excited, passion gives him genius, he discovers relations of which, 

 until that moment he had never had any idea.t " Of two cocks, one was 

 to be opened at the moment when the beam, which Newcomen first 

 introduced into his engines with such effect, had terminated its descend- 

 ing oscillation, and it was obliged to be closed exactly at the end of the 

 opposite oscillation. The management of the second was precisely con- 

 trary. Thus the positions of the beam and those of the cocks was 

 necessarily dependent on each other. Potter took advantage of this re- 

 mark, he observed that the beam could be used to communicate to the 

 other parts, all those movements which the action of the engine re- 

 quired, and immediately carried his conception into execution. The 

 ends of several strings were attached to the handles of the cocks, and 

 the other ends Potter fastened to convenient points of the beam, so that 



• S.tvery liar! already had recourse to a ciineiit of colli water, wliicli he turned 

 upon the exterior gurface of a metal vessel, to condense the steam which this vessel 

 contained. Such was the origin of his association with Newcomen and Cawley, bat 

 it mnst not be forgotten that the patent of Savery, his machines, and the work in 

 which lie describes them, are many years later than the memoir of I'apin. — Note of 

 M.Arayo. 



t A recent carricattire represents some one inviting an Irishman to a dinner of 

 roast beef and potatoes. "Oh!" says tlie li-ishinan, " I have just had a dinner of 

 that same, barrin the meat.'' Tliis seems to be the case with M. Aratjo and his friends, 

 De Oanj and Papin, they contribnted every thing except what was most essential. — 

 Note of the translator. 



1 This is one of those overflown descriptions in which M. Arago delights to in- 

 dulge. A mischievous boy, wanting to plav trnaut, iinmediately becomes a subject 

 of divine inspiration. It is onr dnty to perform our task strictly, so that we feel 

 bonnd to make this ap.doey to our readers for not veiling this phrase in more sobeJ 

 terms. — Note of th^ translator. 



There proceeds also from the bottom of the cylinder a pipe Q, of which the 

 lower end is turned upwards, and is covered with a valve v; this part is im- 

 mersed in a cistern of water called the hot well, and the pipe itself is called 

 the eduction pipe. To regulate the strength of the steam in the boiler, it is 

 furnished with a safety valve, constructed and used in the same manner as 

 that of .Savery's engine, but not loaded with more than one or two pounds on 

 the square inch. 



The mode of operation remains to he described. Let the piston be pulled 

 down to the bottom of the steam cylinder, and shut the regulator or steam 

 valve p. Then the piston will be kept at the bottom bv the pressure of the 

 atmosphere. Apply the fire to the boiler till the steam escapes from the 

 safety valve, and then, on opening the steam regulator, the piston will rise 

 by the joint effect of the strength of the steam, and action of the excess of 

 ■weight on the other end of the beam. When it arrives at the top of the 

 cylinder, close the reijulatorp, and, by turning the injection cock O, admit a 

 jet of cold water, which condenses the steam in the cylinder, forming a par- 

 tial vacuum, and the piston descends by the pressure of the atmosphere, 

 raising water by the pump rod H from the mine. The air which the steam 

 and the injection water contain, is impelled out of the sniffing valve V, by 

 the force of descent, and the injection water flows out at the eduction pipe 

 Q; and by repetition of the operations of alternately admitting steam and 

 injecting water, the work of raising water is effected. — Tredt/old, 



the oscillations of the beam acting on the strings by ascending and de.s- 

 cending, opened and shut the cocks and supplied the place of manual 

 labour ; and for the first time the steam engine acts of itself, for the first 

 time it has no other attendant near it than the stoker, who, from time 

 to time comes to renew and keep up the fuel under the boiler. For the 

 strings of the boy Potter, manufacturers soon substituted rigid vertical 

 rods, fixed to the beam and armed with levers, which press upwaids and 

 downwards the heads of the difl'erent cocks. Th.se rods have now been 

 supplanted by other combinations, but however humiliating the confession 

 may be, all these inventions are simply modifications of the mechanism 

 which was suggested by a boy who wanted to join his playfellows. 



In collections of apparatus there are agood many machines, of the utility 

 of which to manufacturers great hopes have been formed, but which the 

 dearness of their construction, or their maintenance, has reduced to mere 

 curiosities. Such would have been the final lot of Newcumcu's machine, 

 at least in localities deficient in fuel, if the labours of Watt, of which I 

 must now give you an analysis, had not introduced an unexjfected per- 

 fection. "This perfection, however, mu.st not be considered as the result 

 of any casual observation, or of a single ingenious inspiration, for its 

 author arrived at it by assiduous study, and by experiments of extract, 

 dinary beauty and delicacy. 1 1 might be said, that Watt had adopted 

 Bacon's celebrated maxim, " To write, speak, meditate, or act, when we 

 are not well provided with /ac(s to excite our thoughts, is to navigate 

 without a pilot along a coast bristling with dangers ; it is to launch out in 

 the immense ocean without compass or helm." 



There was in the collection of the Tniversity of Glasgow, a small 

 model of Ne^vcomen's steam engine, which had never worked properly. 

 Anderson, the Professor of Natural Philosophy, gave it to Watt to repair. 

 Under the skilful hand of the workman, the faults in its construction dis- 

 appeared, and from that time the model v. orked every year in the lecture 

 room before the wonder-struck students. An ordinary man would have 

 been contented with this success, but Watt, according to custom, unly 

 saw the opportunity for deeper studies. Ills researches were successively 

 directed to every point which seemed to clear up the theory of this ma- 

 chine. He determined the quantity of expansion of the water when it 

 passes from a liquid state to that of steam ; the quantity of water which 

 a given weight of coal can vaporize ; the quantity of steam in weight 

 which one of Newcomen's engines, of known dimensions, consumes at 

 each oscillation ; the quantity of cold water which is necessaiy to be in- 

 jected into the cylinder to give the descending oscillation of the piston 

 a ceitain power; and, finally, the elasticity of steam at different tem- 

 peratures. 



Here was enough to have occupied the life of a laborious mechanic; 

 Wiitt, however, found out the means of succeeding in many and most 

 difliciilt pursuits, without interrupting the labours of the workshop. Dr. 

 Clehmd wished to take me to the house to which our colleague used to 

 retire to make experiments on leaving his shop, but unfoitunately we 

 f'und it pulled down. Our sorrow was great, but of short duration; 

 on the site of the foundation, still existing, ten or twelve hardy 

 labourers, seemed as if sanctifying the birth-place of the modern 

 steam-engine. They were hammering different parts of a boiler, larger 

 certainly than the humble dwelling which formerly adorned the spot. 

 On this site, and in similar circumstances, the most elegant mansion, the 

 finest statue, the most sumptuous monument, would have been less 

 fitting to the genius loci than the gigantic boiler. 



If the properties of steam are still present in your minds, you will per- 

 ceive at once that the economic action of Newcomen's machine requires 

 two irie.'oneilable conditions. When the piston descends, the cylinder 

 must be cold, or it would meet steam still very elastic, which would 

 greatly retard its action and diminish the effect of the external atmos- 

 phere. When, therefore, steam at KKJo C (iil2o F. ) rushes into the 

 same cylinder, if the surfaces are cold this steam warms them by a par- 

 tial liquefaction, and until they acquire a temperature of 100" C. (2I'2o F. ) 

 the elasticity is considerably diminished. The consequence is, a slow- 

 ness in the movements, for the counterpoise does not lift up the pistou 

 l)efore there exists in the cylinder a springiness sufficient to counter- 

 balance the action of the atmosphere. Thence also an increased ex- 

 pense, since, as I have explained, steam is very dear. We shall see 

 directly the immense importance of this economic consideration, when I 

 inform you that the Glasgow model used at each oscillation a volume of 

 steam several times greater than that of the cylinder. Ihe expense of 

 the steam, or, what comes to the same, of the fuel, or, rather, if you 

 prefer it, the indispensable pecuniary expense of maintaining the move- 

 ment of the machine, would be several limes less if we could get rid of 

 those successive coolings and healings, the inconveniences of which I 

 have pointed out. 



This problem, apparently insolvable. Watt resolved by the simplest 

 means. He found it sufficient to add to the former disposition of the 

 machinery a vessel distinct from the cylinder, and only communicating 

 with it by means of a narrow tube provided with a cock. This vessel, 

 which is now called a co/if/t'H.wr, is Watt's principal invention, and not- 

 withstanding my desiie to shorten the subject, I cannot avoid explaining 

 its action. 



( To be continued. ) 



