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CHAPTER EIGHTH.

"IN PROPORTION AS EXCELLENT PRODUCTIONS SHALI. MULTIPLY, EVERY SUCCESSIVE GENERATION OF MEN WILL DIRECT ITS ATTENTION TO THOSE WHICH ARE MOST PERFECT, AND THE REST WILL INSENSIBLY FALL INTO OBLIVION. BUT THE MORE SIMPLE AND PALPABLE TRAITS WHICH WERE SEIZED BY THOSE WHO FIRST ENTERED THE FIELD OF INVENTION, WILL NOT THE LESS EXIST FOR POSTERITY, THOUGH FOUND ONLY IN THE LATEST PRODUCTION."-Condorcet.

THE knowledge of the construction and peculiarities of steam-machinery, extending by degrees among classes less directly interested in it, as a subject for mechanical practice, than for the purpose of philosophical illustration, had given rise to an opinion, that its invention sprung from scientific deduction. But Desaguliers ridicules this notion of its origin : " if," says he, "it is imagined, that it must be owing to great sagacity, and a thorough knowledge of philosophy, that such proper remedies for the inconveniences and difficult cases were thought of, here has been no such thing, almost every improvement has been owing to chance." And it was probably waiting for similar good fortune, that many parts of the machinery were left by later mechanics to chance for their further improvement.

Great care and no small ingenuity had been expended on the cylinder and its appendages; the boiler had received a portion of attention, and its

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IMPROVERS OF ENGINES.

shape was regulated by geometrical canons, and the furnace, too, was not quite forgotten, for the smoke flue was made to meander, in every possible way, round the boiler; and it may have been that its meanderings were advantageous. But the circumstances which mainly effected the general loss of power not being agreed upon, opened a field of contention, which was at all times fully occupied. "The attendant," said one improver," is careless, and he does not feed the fire so copiously as he should. A large furnace-ample surface of grate-bar and plenty of coal, what more is necessary?—if a failure of effect is still apparent, let the coal-binn be examined, and judgment given to bury the lazy or niggardly engine-man under his miscalled savings. My furnace will consume any thing, and raise steam in an hour sufficient for a day." "But it will do better," says a second, "if my boiler is placed over it." "Without my piston and steam valve," says a third," in my opinion, your schemes will prove abortive." And thus rival mechanists carried on a petty warfare, each depreciating his neighbour's nostrum, and earnestly recommending his own. There was however one fact acknowledged by all -enormous quantities of coals were engulphed in the furnace.

It was a boast with those who were interested in the erection of this kind of machinery, that the great expenses incurred for draining coal mines were absolutely saved altogether by using the fire-engine-for it may be worked, they said, with the refuse of the produce of the mine which is not only unsaleable, but whose accumulation on the surface is a positive nuisance.

Whatever shadowings of truth gave relief to this statement, experience quickly taught, that in the most favourable cases, the economical advan

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tage was bounded within narrow limits ;-and the furnace of a fire-engine, even at the mouth of a coal mine was like other monsters, whose voracity, although it might partly be satisfied by devouring garbage, required to be often stimulated by substances of more value;-and the "good coal, the market article," that was thrown in, to propitiate, as it were, "the refuse" to do its office, became a serious item of deduction from the gross profit:where the whole supply was to be brought from a distance, and bought at a high price, the consumption of fuel was beheld with astonishment, and the worldly-minded proprietor, on reckoning up its value, was struck with dismay.

The first attempt to form an estimate of the quantity of fuel, that ought not to have been thrown into the "burning fiery furnace," by observing how much made its exit in the primitive state at the chimney-top, was made by a Doctor John Allen, in a book, which he published in 1730. He found, that "in the common method of boiling water (since the invention of setting boilers in furnaces) by the application of fire under the bottom, and round the sides of the boilers, notwithstanding how much soever it may exceed the boiling of water in a kettle over an open fire, it is evident, that well-nigh half of the heat or effect of the fire is employed in heating the walls of the fire-place; and in the best contrived furnaces that he ever saw, the current of flame and heat, after having fetched one single compass by a flue round the boiler, made its exit presently into the tunnel, whence it escaped into the air, and further benefit and advantage was entirely lost."

In his experiments to provide a remedy for this * Specimina Ichnographia, or a brief narrative of several new inventions. London, 1730.

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