1S39.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



401 



thoroughly appreciated, without having recourse to tedious numerical 

 comparisons. In order that these comparisons, if rendered indispensable, 

 rray be easily understood, I will allude as biietly as possible to the beau- 

 tiful physical laws upon which it will be necessary to base them. 



By means of simple changes of temperature, water may exist in three 

 perfectly distinct states ; in the solid state, the liquid state, and the 

 «rial or gaseous state. Below zero, of the centigrade thermometer, 

 (:32°F) water becomes ice; at 100° (-il'l"?) it is rapidly converted into 

 gas; in all the intermediate degrees it is liquid. 



A scrupulous observation of the points of transition from one of these 

 states to another, leads to first-rate discoveries, which are the keys to 

 the economical doctrines of the steam-engine. 



Water is not necessarily botter than any kind of ice, for it may be kept 

 at the temperature of zero (3"2°F) without freezing; while ice may re- 

 main at zero (3-.i°F) without melting; but it seems difficult to believe 

 that water and ice, both of the same degree of temperature, both being 

 at zero, only differ in their physical propeities; that any element foreign 

 to water, properly so called, cannot make a distinction between solid 

 water and liquid water. A very simple experiment will, however, clear 

 up the mystery. 



Mix a pound of water at zero (3'2°F), with a pound of water at 75° 

 centigrade, (I67°F); the two pounds of the mixture will be at 37^° 

 {99^°F), that is to say, at the medium temperature of the two component 

 liquids. You thus perceive that the warm water has retained 372° of its 

 former temperature, whilst it has yielded the other 37.^° to the cold 

 water ; all that is natural, and what might easily be forseen. 



But let us now repeat the experiment with a single modification ; 

 instead of the pound of water at zero (32° F), let us take a pound of ice 

 at the like temperature of zero, (32° F). From the mixture of this pound 

 of ice with the pound of water at 75" ( 167°F), will result two pounds of 

 liquid water, since the ice steeped in the warm water cannot fail to be 

 melted, and it will keep its former weight. But do not h stily attribute 

 to the mixture, as before, a temperature of 37^°, (d9\" F. ) tor this will 

 lead to an error: the temperature will be that of zero only. No trace 

 will remain of the 7J° (167"^ F. ) of heat that the pound of water pos- 

 essed. These 73° (IG?" F.) will have disunited the particles of ice, and 

 have combined with them, but without warming them in any way, 



I do not hesitate to pronounce this experiment of Black one of the 

 most remarkable in modern natural philosophy. Look, indeed, at its 

 consequences : 



Water at zero, and ice at zero, (32" F. ) differ in their intimate com- 

 position. The liquid comprises 75° (167" F.) of an imponderable sub- 

 stance, called heat, more than the solid. These 75° ( 167" F. ) are so well 

 concealed iii/'the composition, I had almost said in the aqueous alliance, 

 that the finest thermometer does not discover its existence. Heat, im- 

 perceptible to our senses, impercei)tible to even the most delicate instru- 

 ments ; in short, latent heat, for that is the name given to it, is one of 

 the principal constituents of bodies. 



The comparison of bulling water, of water at 100° (212°F), with the 

 steam which dies off, and also of a temperature of 100° (212" F, ), leads to 

 like results, but on a grander scale. At the time of being converted to a 

 state of vapour at 100" (212" F), water becomes impregnated under a 

 latent form, under a form not perceptible to the thermometer, with 

 an enormous quantity of heat. When steam resumes the liquid state, 

 this heat is disengaged, and goes to warm every thing, on its way, 

 susceptible of absorbing it. If, for example, you cause a single pound of 

 steam at 100" (212" F) to pass through 5u 35 pounds of water at zero, the 

 steam will become quite liquified. The 6" 35 pounds resulting from the 

 mixture are at a temperature of lOCo (212" F). There enters then into the 

 intima'e composition of a ]>ound of steam, a quantity of latent heat 

 which would raise a pound of water, if prevented from evaporating, from 

 to 535" centigrade., (964" F.) This result will certainly appear 

 enormous, but it admits of no doubt. Steam only exists on these con- 

 ditions : wherever a pound of water at zero (32" F) is converted into 

 steam, either naturally or artificially, it should take, to effect ihe change, 

 and it does in fact take Irom the surrounding bodies, 535" (904" F) 

 of beat. It cannot be too often repeated, that steam, in fact, restores 

 these degrees upon whatever surfaces its ultimate liquifaclion is atfected. 

 This is, indeed, the whole artifice from the fuel to the steam. They but 

 badly comprehend this ingenious process, who imagine that aqueous gas 

 oidy conveys to the pipes^ in which it circulates, perceptible or thermome- 

 trical heat; the principal effects are duo to component heat, to hidden 

 heat, to latent heat, which is disengaged at the moment, when the steam, 

 by coming in contact with cold surfaces, is converted from a gaseous to a 

 liquid state. 



Henceforth, we must rank heat among the principal constituents of 

 steam. We can only obtain heat by burning wood or coal. Steam, 

 therefore, bears a market price higher than water, by the cost of the fuel 

 employed in the act of vaporization/ If the diHerence of the two values 

 is very great, you must principally attribute it to latent heat, for ther- 

 mometrical or sensible heat only bears a very small proportion to it. 



Perhaps, at a later period, I shall have to dwell on some of the other 

 properties of steam, so that if I do not mention them now, you must not 

 imagine that I attribute to this assembly the disposition of certain stu- 

 dents, who once said to their professor of geometry : " Why do you take 

 " so much trouble to demonstrate these theorems ? We have the fullest 

 " confidence in you ; give us your word of honor that they are true, and 



2 K2 



" that will be enough I " But I must not abuse your indu'gence ; I must 

 bear in mind, that by referring to special treatises, you can easily fill the 

 gaps which I have been obliged to leave. 



Let us now endeavour to determine the position of those nations 

 which appear deserving of notice in the history of the steam-engine ; 

 let us trace the chronological series of improvements which this machine 

 has undergone from its first glimmerings, now almost forgotten, down 

 to the brilliant discoveries of V\'att. I take up this subject with the fixed 

 determination of being impartial; with a strong desire of rendering to 

 every inventor that justice which is due to him ; and with the certainty 

 of remaining independent of every consideration whicti should or may 

 originate in national jirejudice, alike unworthy of the mission intrusted to 

 me, alike unworthy of the majesty of science. I admit, on the other 

 hand, that I shall pay but little attention to the numerous decisions 

 passed under the dictation of similar prejudices ; and, if possible, I shall 

 beed still less, the severe criticisms which undoubtedly await me, for it 

 is seldom in things of this nature that the future does not resemble the 

 past. 



A question well put is half resolved. If this sensible maxim had been 

 borne in mind, certainly, the discussion on the invention of the steam- 

 engine would not have assumed that acrimonious and violent character, 

 withwhichuntil now it has been so strongly impressed. But, in endeavour- 

 ing to single out one inventor, where, of necessity, several should have been 

 distinguished, people rashly cast themselves into a defile, without an out- 

 let ; a watchmaker, well acquainted with the history of his art, would 

 be obliged to hold his tongue before any one who asked him, in general 

 terms, who invented watches ; on the other hand, he would be but 

 little embarrassed by the question, if it related separately to the motion, 

 to different forms of the escapement, or to the balance— so thus it is 

 with the steam-engine -. it presents, at this day, the realization of several 

 original, but very distinct ideas, «hich could not have emanated from the 

 same source, but out of which, it is still our duty carefully to search the 

 origin and date. 



If, having made any use whatever of steam would give, as has bern 

 pretended, a right to figure in the history of this invention, we should bo 

 obliged to assign the first place to the Arabians, since, fiom time imme- 

 morial, their principal food, which they call couscoiissou, has been cooked 

 by the action of steam on strainers, placed over rude kettles. A result like 

 this is quite sufficient to t1u-ow back all the ridicule upon the source from 

 which it was derived. Did Gerbert, our fellow countryman, who wore 

 the triple crown under the name of Sylvester II., acquire a greater, 

 when, towards the middle of the ninth century, he made the pipes of the 

 oigan of the cathedral of Rheims sound by the aid of steam? I do not 

 think so : in the instrument, fashioned by the future pope, I can only 

 discover a current of steam substituted for a current of ordinary air, 

 the production of the musical phenomenon in the pipes of the organ, 

 but in no wise a mechanical effect, properly so called. 1 find the first 

 example of motion, engendered by steam, in a toy* still more ancient 

 than the oigan of Gerbert ; in an eolipile of Hero of Alexandria, the 

 date of which goes back to 120 years before our era. Perhaps it would 

 be difficult, without the aid of a figure, to give a clear idea of the mode 

 of action of this little instrument; but I shall try. 



When the gas escapes, in a cert.iin way, from the vessel which con- 

 tains it, this vessel, by means of rc-action, tends to move in a diame- 

 trically opposite direction. The recoil of a gun, loaded with powder, is 

 on the same principle ; the gas, engendered by the inflammation of the 

 saltpetre, charcoal, and sulphur, flies off in the air, according to the direc- 

 tion of the barrel ; the direction of the gun, lengthened backwards, 

 abuts on the shoulder of the person who fired ; it is, then, upon the 

 shoulder that the butt end should re-act with force. To change the direc- 

 tion of the recoil, it is sufficient to cause the stream of gas to fiOW out; 

 in another direction. If the barrel were stopped at its mouth, and vveie 

 only pierced with a lateral opening, perpendicular to its direction, and 

 horizontal, the gas of the powder would escape laterally and horizontally ; 

 and the recoil would act perpendicularly to the barrel ; it would be felt 

 on the arm and not on the shoulder. In the first case, the recoil would 

 push the peison who fired, backwards, as if to overturn him ; but in the 



* Hero's Sleam Tui/.—A motion round an axis is elegantly given; 

 globe, by means of the re-action of steam upon the 

 air. Two pipes, a, c, each having their upper extre- 

 mity bent towards each other, rise from the cover of 

 a vase, o ; one of the^e, c, acts merely as a pivot, 

 the other, a, conducts steam, raised in the boiler, 

 into the ball or globe, i. This is suspended between 

 them by having the steam-pipe, a, inserted into it, 

 and is kept in its position by the pivot formed at the 

 end of the opposite pipe, c. Two pipes, in, n, also 

 bent at right angles at tliei* extremities, are inserted 

 into the circumference of the globe, and form a com- 

 munication between the cauldron and the atmosphere. 



Heat being applied to the cauldron, tlie steam, fiow- 

 ing from it through the vertical pipe o, into the little 

 globe, !, thence linds its way through the pipes or 

 arms, m, n, into the atmosphere ; at this instant the 

 re-action of the vapour on the air makes the globe 

 revolve with a magical celerity, '* as if it were ani- 

 mated from within by a living spirit," — Stuart, 

 i 



to a small 



