The Steam Engine Familiarly Explained and Illustrated. Dionysius Lardner
of the progressive developement of those physical principles on which the steam engine depends, and of their mechanical application, has of late years received some importance, as well from the interest which the public manifest towards them as from the rank of the writers who have investigated them, we have thought it expedient to state briefly, but we trust with candour and fairness, the successive steps which appear to have led to this invention.
The engine as it exists at present is not, strictly speaking, the exclusive invention of any one individual: it is the result of a series of discoveries and inventions which have for the last two centuries been accumulating. When we attempt to trace back its history, and to determine its first inventor, we experience the same difficulty as is felt in tracing the head of a great river: as we ascend its course, we are embarrassed by the variety of its tributary streams, and find it impossible to decide which of those channels into which it ramifies ought to be regarded as the principal stream; and it terminates at length in a number of threads of water, each in itself so insignificant as to be unworthy of being regarded as the source of the majestic object which has excited the inquiry.
From a very early period the effects of heat upon liquids, and more especially the production of steam or vapour, was regarded as a probable source of mechanical power, and numerous speculators directed their attention to it, and exerted their inventive faculties to derive from it an effective mover. It was not, however, until the commencement of the eighteenth century that any invention was produced which was practically applied, even unsuccessfully. All the attempts previous to that time were either suggestions which were limited to paper or experiments confined to models; or, if they exceeded this, they never outlived a single trial on a larger scale. Nevertheless many of these suggestions and experiments being recorded and accessible to future inquirers doubtless offered useful hints and some practical aid to those more successful investigators who subsequently contrived engines in such forms as to be practically available on a large scale for mechanical purposes. It is right and just, therefore—mere suggestions and abortive experiments though they may have been—to record them, that each inventor and discoverer may receive the just credit due to his share in this splendid mechanical invention. We shall then in the present chapter briefly enumerate, in chronological order, the successive steps so far as they have come to our knowledge.
HERO OF ALEXANDRIA, 120 BC
Fig.1.
(23.) In a work entitled Spiritalia seu Pneumatica, one of the numerous works of this philosopher which has remained to us, is contained a description of a machine moved by vapour of water. A hollow sphere, of which A B represents a section, is supported on two pivots at A and B, which are the extremities of tubes A C D and B E F, which pass into a boiler where steam is generated. This steam flows through small apertures at the extremities A and B, and fills the hollow sphere. One or more horizontal arms K G, I H, project from this sphere, and are likewise filled with steam, but are closed at their extremities. Conceive a small hole made near the extremity G, but at one side of one of the tubes; the steam confined in the tube and globe would immediately rush from the hole with a force proportionate to its pressure within the globe. On the common principle of mechanics a re-action would be produced, and the tube would recoil in the same manner as a gun when discharged. The tubular arm K G being thus pressed in a direction opposed to that in which the steam issues, the sphere would revolve accordingly, and would continue to revolve so long as the steam would continue to flow from the aperture. The force of recoil would be increased by making a similar aperture in two or more arms, care being taken that all the apertures should be placed so as to cause the sphere to revolve in the same direction.
This motion being once produced might be transmitted by ordinary mechanical contrivance to any machinery which its power might be adequate to move.
This method of using steam is not adopted in any part or any form of the modern steam engine.
BLASCO DE GARAY, AD 1543.
(24.) In the year 1826 there appeared in Zach's Correspondence a communication from Thomas Gonsalez, Director of the Royal Archives of Simancas, giving an account of an experiment reported to have been made in the year 1543 by order of Charles V. in the port of Barcelona. Blasco de Garay, a sea captain, had contrived a machine by which he proposed to propel vessels without oars or sails. Garay concealed altogether the nature of the machine which he used: all that was seen during the experiment was that it consisted of a great boiler for water, and that wheels were kept in revolution at each side of the vessel. The experiment was made upon a vessel called the Trinity, of 200 tons burden, and was witnessed by several official personages, whose presence on the occasion was commanded by the king. One of the witnesses reported that it was capable of moving the vessel at the rate of two leagues in three hours, that the machine was too complicated and expensive, and was exposed to the danger of explosion. The other witnesses, however, reported more favourably. The result of the experiment was thought to be favourable: the inventor was promoted, and received a pecuniary reward, besides having all his expenses defrayed.
From the circumstance of the nature of the impelling power having been concealed by the inventor it is impossible to say in what this machine consisted, or even whether steam exerted any agency whatever in it, or, if it did, whether it might not have been, as was most probably the case, a reproduction of Hero's contrivance. It is rather unfavourable to the claims advanced by the advocates of the Spaniard, that although it is admitted that he was rewarded and promoted in consequence of the experiment, yet it does not appear that it was again tried, much less brought into practical use.
SOLOMON DE CAUS, 1615.
Fig.2.
(25.) A work entitled "Les Raisons des Forces Mouvantes, avec diverses Machines tant utiles que plaisantes," published at Frankfort in 1615, by Solomon de Caus, a native of France, contains the following theorem:—
"Water will mount by the help of fire higher than its level," which is explained and proved in the following terms:—
"The third method of raising water is by the aid of fire. On this principle may be constructed various machines: I shall here describe one. Let a ball of copper marked A, well soldered in every part, to which is attached a tube and stopcock marked D, by which water may be introduced; and also another tube marked B C, which will be soldered into the top of the ball, and the lower end C of which shall descend nearly to the bottom of the ball without touching it. Let the said ball be filled with water through the tube D, then shutting the stopcock D, and opening the stopcock in the vertical tube B C, let the ball be placed upon a fire, the heat acting upon the said ball will cause the water to rise in the tube B C."
Such is the description of the apparatus of De Caus as given by himself; and on this has been founded a claim to the invention of the steam engine. It will be observed, that neither in the original theorem nor in the description of the machine which accompanies it, is the word steam anywhere used. Now it was well known, by all conversant in physics, long before the date of the publication containing this description, that atmospheric air when heated acquires an increased elastic force. As the experiment is described, the other part of the ball A is filled with atmospheric air; the heat of the fire acting upon the air through the external surface of the ball, and likewise transmitted through the water, would of course raise the temperature of the air contained in the vessel, would thereby increase its elasticity, and would cause the water to rise in the tube B C, upon a physical principle altogether independent