fire, and a little after pour out the water at the hole, and it will be found that a part of the said water has been evaporated by the heat of the fire. Then pour in one pot of water as before, and stop up the hole and the cock, and put the vessel on the fire for the same time as before; then take it off, and let it cool of itself, without opening the plug, and after it is quite cold pour out the water, and it will be found exactly the same quantity as was put in. Thus we see that the water which was evaporated (the first time that the vessel was put on the fire) is returned into water the second time when that vapour has been shut up in the vessel, and cooled of itself."

In the description of these experiments, the processes of evaporation and condensation are obscurely indicated; but there is no intimation that the author possessed any knowledge of the elastic force of steam. His theorem is, that the parts of the element water mix for a time with the parts of the element air; that fire causes this mixture, and that on removing the fire, and dissipating the heat, then the parts of the water mixed with air return to their proper place, forming again part of the water. There is no indication of a change of property of the water in passing into vapour. It is difficult to conceive, if De Caus had been aware that the vapour of water possessed the same violent force which he distinctly and in terms ascribes to air, or if he had been aware that in effect the vapour of the water produced by the fire was a fluid, possessing exactly the same mechanical qualities, and producing the same mechanical effects as air, that he would not have expressed himself clearly on the subject.

He proceeds to give another demonstration that heat will cause the particles of water to mix with those of air.

"After having put the measure of water into the vessel, and shut the vent-hole, and opened the cock, put the vessel on the fire, and put the pot under the cock; then the water of the vessel, raising itself by the heat of the fire, will run out through the cock; but about one sixth or one eighth part of the water will not run out, because the violence of the vapour which causes the water to rise proceeds rom the

said water; which vapour goes out through the cock after the water with great violence. There is also another example in quicksilver, or mercury, which is a fluid mineral, but being heated by fire, exhales in vapour, and mixes with the air for a time; but after the said vapour is cooled, it returns to its first nature of quicksilver. The vapour of water is much lighter, and therefore it rises higher," &c. &c.

In this second demonstration there appears to be some obscure indication of the force of steam in the words "because of the violence of the vapour which causes the water to rise," &c.

The fifth theorem is the following:

B

ก

A

Fig. 2.

"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 stop-cock marked D, by which water may be introduced; and also another tube marked в 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 stop-cock D, and opening the stop-cock in the vertical tube в 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."

In the apparatus as here described, the space enclosed in the boiler above the surface of the water is filled with air. By the action of the fire, two effects are produced: first, the air enclosed above the water, being heated, acquires increased elasticity, and presses with a corresponding force on the surface of the water. By this means a column of water will be driven up the tube A B at such a height as will balance the elasticity of the heated air confined in the boiler; but besides

this the water contained in the boiler being heated, will produce steam, which being mixed with air contained in the boiler, will likewise press with its proper elasticity on the surface of the water, and will combine with the air in raising a column of water in the tube A B. In the above description of the machine, the force which raises the water in the tube A B is ascribed to the fire, no mention being made of the water, or of the vapour or steam produced from it having any agency in raising the water in the tube a B.

Antecedently to the date of this invention, the effect of heat in increasing the elastic force of air was known, and so far as the above description goes, the whole operation might be ascribed to the air by a person having no knowledge whatever of the elasticity of steam. M. Arago, however, who, on the grounds of this passage in the work of De Caus, claims for him a share of the honour of the invention of the steam engine, contends that the agency of steam in this apparatus was perfectly known to De Caus, although no mention is made of steam in the above description, because in the second demonstration above quoted he uses the words, "the violence of the vapour which causes the water to rise proceeds from the said water; which vapour goes out from the cock after the water with great violence." By these words M. Arago considers that De Caus expresses the quality of elasticity proper to the vapour, and that the context justifies the inference, that to this elasticity he ascribed the elevation of the water in the tube C B.

There appears to be some uncertainty attending the birthplace of De Caus. In the Biographie Universelle he is said to have been born and to have died in Normandy. M. Arago assigns Dieppe, or its neighbourhood, as his birthplace. There was another engineer and architect, Isaac De Caus, a native of Dieppe, who published a work in folio, entitled "Nouvelle Invention de Lever l'Eau plus haut que sa Source, avec quelque Machines mouvantes, par le Moyen de l'Eau, et un Discours de la Conduite d'Icelle." This volume is without a date, but from the nature of its contents it would appear to have been published before the work of Solomon De Caus already cited. The drawings and machines described in both

are exactly the same; but the definitions and theorems quoted above on raising water by fire are not given in the work of Isaac. It seems, therefore, that Solomon De Caus re-published, with additions, the work of Isaac De Caus. From the same birthplace being assigned to both these authors, as well as from the similarity of their pursuits, it is likely they were members of the same family, and from their christian names they were probably Jews.

The work cited above, was dedicated to Louis XIII., and in the dedication Solomon De Caus calls himself the subject of that monarch; and in the privilege prefixed to the work he is designated, "Our well-beloved Solomon De Caus, master engineer, being at present in the service of our dear and well-beloved cousin, the Prince Elector Palatine, has made known to us," &c.-"we, desiring to gratify the said De Caus, he being our subject," &c.

It is therefore certain, whatever may have been the birthplace of De Caus, that he was at least a subject of France. The circumstance of his work being written in French, though published beyond the Rhine, is also an argument in favour of his being a native of that country.

GIOVANNI BRANCA, 1629.

(6.) Giovanni Branca of Loretto in Italy, an engineer and architect, proposed to work mills of different kinds by steam issuing from a large æolopile, and blowing against the vanes of a wheel. Branca was the author of many ingenious mechanical inventions, a collection of which he dedicated to M. Cenci, the governor of Loretto. These were published in a work printed at Rome in 1629. It is a thin quarto, entitled "Le Machine volume nuovo, et di molto artificio da fare effetti maravigliosi tanto Spiritali quanto di Animale Operatione, arichito di bellissime figure. Del Sig. Giovanni Branca, Cittadino RoIn Roma, 1629." The work contains sixty-three engravings, accompanied by descriptions in Italian and Latin. Branca's steam engine, represented in the twenty-fifth plate, consists of a wheel furnished with flat vanes upon its rim, like the boards of a paddle wheel. The steam is produced in a close vessel, and made to issue with violence from the ex

mano.

tremity of a pipe directed against the vanes, and causes the wheel to revolve. This motion being imparted by the usual mechanical contrivances, any machinery may be impelled by it. Different useful applications of this power are contained in the work, viz. pestles and mortars for pounding materials to make gunpowder, and rolling stones for grinding the same; machines for raising water by buckets, for sawing timbers, for driving piles, &c. &c.

This method of applying the force of steam has no analogy to any application of steam in modern engines.

EDWARD SOMERSET, MARQUIS OF WORCESTER, 1663.

(7.) Of all the names which figure in the early annals of steam, by far the most remarkable is that of the Marquis of Worcester, who has left a description of a machine in a work, entitled "The Scantling of One Hundred Inventions," which has been generally in this country considered as giving him a right to the honour of having been the inventor of the steam engine.

Lord Worcester having been engaged on the side of the Royalists in the civil wars of the revolution, lost his fortune, and went to Ireland, where he was imprisoned. He escaped from thence, and reached France; from that country he ventured to London, as a secret agent of Charles II., but was detected, and imprisoned in the Tower, where he remained until the restoration, when he was set at liberty. Tradition has connected the invention of the steam engine with the following anecdote:- One day, during his imprisonment, Lord Worcester observed the lid of the pot in which his dinner was being cooked, suddenly forced upwards by the vapour of the water which was boiling in it. Reflecting on this, it occurred to him that the same force which raised the cover of the pot might be rendered, when properly applied, a useful and convenient moving power. After he recovered his liberty, he accordingly proceeded to carry into effect this conception. The contrivance to which he was ultimately led is described in the following terms in the sixty-eighth invention, in the work above named :

"I have invented an admirable and forcible way to drive