was described in a book printed at Leipsig. It consisted of a globe with two necks, or outlets on opposite sides; a small quantity of water was introduced into it, and rarefied into steam by a fire made under it; the vapour issued then at the two necks, and by its reaction a continuous motion was generated.

In 1624, Solomon de Caus, a French engineer, described an engine acting by the elasticity of steam; but the first person who in modern times applied it on any scale, to a useful practical purpose, . was Giovanni Branca, who resided at Rome in the beginning of the seventeenth century. A description of his engine (which was only an improved Oelipile) from the pen of Mr. Partington, has already been given in our 9th Number. Mr. Stuart adds, with truth, however, that to the merit of a first idea; assigned to him by Mr. Partington, Branca has no claim.

The elasticity of the vapour of water, which had now become familiar to water-work artists, was applied by them in a variety of ways to their favourite problem of raising water above its level in jets and fountains.

Mr. Stuart describes two of these Air Engines, as they were called, but very prudently, "without vouching for the great effects" said to have been produced by them.

"for

Bishop Wilkins, in his Mathematical Magic, 1648, speaks of the Oclipiles as if in his time, and in England it had been extensively applied to useful purposes. "These are frequently used," he says, exciting and contracting of heat in the melting of glasses or metals.* They may also be contrived for sundry other pleasant uses; as for moving the sails in a chimney corner; the motion of which sails may be applied to the turning of a spit, or the like."

We come next to the pretensions of the Marquis of Worcester, who, of "all those whose names are associated with the history of the steam

An authority, by-the-bye, in favour of our Goldsmith's Apprentice Steam Soldering Machine.-Soe p. 273, Vol. [Y.

engine in its infant stages, is by far the most celebrated."

Mr. Stewart differs from all the writers who have preceded him in his estimate of the Marquis's merits; he scouts the idea of his having invented the engine, and thinks him merely entitled to some mention, as the probable projector of an improvement in it.'

Since the performances of Hero, De 'Caus, and Branca have been brought to light, there can now be no doubt that the claims of the Marquis have been overrated; but not certainly to the extent represented by Mr. Stewart, whose acuteness on the subject is more to be admired than his liberality. Intending in an early Number to enter upon a full review of the whole of the Marquis's Century of Inventions, we shall defer till then the farther remarks. we have to make on this part of Mr. Stuart's volume.

The author next describes the successive applications of steam, attempted by Sir Samuel Morland (1682), Papin, Amonton, and Savery, to all of whom, particularly the last, full justice is done.

"In his address and explanations, Savery proceeds with all the candour and earnestness of a man, conscious of having made a discovery of immense importauce to mankind; and there is no greater instance of so open and candid an appeal to experiment, and an examination of the actual performance of an engine as a test of its merit in the history of mechanical inventions.

"This engine Savery applied for raising water for palaces, gentlemen's houses with water in general, and pump. scats, draining fens, and supplying ing water from ships; and he erected many of them in different parts of England. The power of his engine he limited only by the strength of the pipes and vessels; for (he says) I will raise you water 500 or 1,000 feet big, could you find us a way to procure strength enough for such an immense weight as a pillar of water that height:"

*

"The advantage derived from the use of Savery's engine, as a substitute for manual labour, was counterbalanced in public opinion by the great risk of accident from an explosion of the boiler;

for, during the term of his patent, it does not appear that he availed himself of the security arising from the use of Papin's Saftely Valve.

Various attempts were made to strengthen the boilers, by radiating arms fixed in the inside, but without any successful resuit: so that, at this period, the only use to which Savery's apparatus could be applied with safety, was to raise water to heights not exceeding 30 or 32 feet-a virtual abandonment of its pretensions as a mine-draining power, which was the grand object of all Savery's exertions"

Then came the improvements of Newcomen the blacksmith, and Cawley the glazier, who "made the experiment of introducing steam under a piston moving in a cylinder and formed a vacuum, by condensing the steam by an effusion of cold water on the outside of the steam-vessel; so that the weight of the atmosphere pressed the piston to the bottom of the cylinder. This was the first form of the atmospheric-engine, the simplest and most powerful machine that had hitherto been constructed."

Still many inconveniences remained to be removed; and not the least was the necessity of employing boys or men to open and shut some of the cocks; for although the risk of accident from the explosion of the boiler might now be considered as obviated, yet the effect of the engine depending inuch on the condition of its parts, and these being rarely deranged by slight irregularities in their action, the danger of injury to the machine itself was considerably increased from the ignorance or carelessness of the attendants.

The mechanism for opening and shutting the cocks also remained perplexed by latches and strings until Mr. Henry Beighton, an engineer, extensively employed in the construction of machinery, erected an engine at Newcastle-on-Tyne in 1718, in which all these "cock-boys" and complication of cords were superseded by a rod suspended from the beam which operated as a mechanism invented by bim called hand-gear; a contrivance, with some slight modifications, employed in engines of the present day. It would also appear that the steel

yard safety-valve was first used in the boiler of this engine, having been suggested to Beighton by Desaguliers.

Mr. Stuart's description of Beighton's engine we shall quote at length; as it will not only give our readers a complete idea of its most approved form of construction at that period, but show more clearly the value of the improvements introduced by that ingenious engineer.

For the use of the illustrative engravings, we are indebted to the kindness of Mr. Stuart, whose ability as a draughtsman is not the least of his merits.

"The cylinder of the Griff Engine was 22 inches in diameter; and Beighton calculated that it contained 113 gallons of steam at every stroke, equal to about 14,464 gallons per minute, which vas produced from about five pints of water; and this quantity was equal in, its performance to three-fourths of the atmospheric pressure; so that, making ailowance for the friction of the piston,, levers, and other parts, about eight pounds of water was raised by each square inch of the piston.

"In examining the seventeenth (our first) figure, which is a view of the Atmospheric Engine as improved by Beighton, it will be seen, that, in addition to the hand-gear, he gave a better. arrangement and form to the parts already in use, and paid more attention to the proportion of the parts among themselves, and to the work which they had to perform; besides introducing greater neatness and accuracy of workmanship into his engines than had been attempted by his predecessors.

"In the seventeenth figure, the cistern,, for the supply of injection water, is placed as in the previous engravings, and water is pumped into it by a small pump connected with the pipe y y, leading from the mine. (The lever beam, 2, is not continued on the pump side beyond its axis A, as this would have required our figure to have been drawn on a scale much too small for being distinct.) To make the piston, d, air-tight, a ring or piece of match↑ is

• “Tallow was used in these engines to lessen the friction, but not to keep them air-tight."

The origin of packing the piston is thus given by Desaguliers: - Having screwed a large broad piece of leather to the piston which turned up the sides of

spanner p, that the weight of the head of the Y picce is brought so far from under n, as to have past the perpendicular to the axle; and being ready to fall over towards m, its shank D, will strike the pin 4, of the stirrup, with a smart blow, and drawing the fork m m, horizontally towards the plug-frame, will also draw the end, o, of the laudle of the regulator v (which slides on the bar between and a), and thereby shut off the communication between the cylinder and the boiler. The fall of the plug-frame will reverse this motion. The moment this movement is completed, the pin 3, on the outside of the plug-frame, depresses the lever, x, attached to the quadrant of a wheel g, which moves another quadrant f, which is fixed on the axis or spindle of the cock, e, of the injection-pipe bc. This, admitting cold water into the cylinder, condenses the vapour, and produces a vacuum; and the pressure of the atmosphere carries the steam-piston downwards, and raises the plug-frame. The lever, , is raised by another pin, which shuts the injection-cock, and depressing one of the spanners fixed on the irou axle, moves the stirrup and fork into the fosition which opens the sliding valve, and peribits the steam again to issue from the boiler into the cylinder.

"The nineteenth (our third) figure is a geometrical view of the same engine, slightly varied in some of its details, and which on the whole may be considered as improvements. As its action is the same as those we have already described, an enumeration of the names of the parts will be sufficient to explain their uses. His the fire-place under the boiler W; ii are the two gauge-cocks; o, the spindle of the regulator valve, which opens or shuts the communication between the cylinder and boiler by the throat-pipe e; the pipe carries the beated injection water into the well; from this pipe, a small branch g proceeds with a funnel-cup, having a valve opening upwards; the hot injection water passes from this into the boiler, and an additional supply is procured by the pipe b, from the cup containing the water used to make the steam-piston airtight; rr is the plug-frame; pp, the spanners, moving the fork, and lever of the regulating valve o, which is constructed somewhat differently in this from the preceding figure; m is the tumbling bob, which has the same use and operation as the Y piece. The injection-cock k is moved by a similar contrivance of a fork acting on the end of a lever, and which is put in action by pins fixed in the plug-frame, to move the