APPENDIX.

A

MONG the variety of improvements that may be fuggefted for the intereft of Mining, thofe certainly are most beneficial, which tend to the perfection of mechanicks and hydraulicks; for had there not been great progrefs made in those branches of philofophy within the laft improved ages of science, Mining would ftill confift of merely digging a few fathoms deep, and raising the stuff and water, by dint of human labour.

About four-score years back, small wheels of twelve or fifteen feet diameter, were thought the best machinery for draining the Mines; and if one or two were infufficient, more were often applied to that purpose, all worked by the fame stream of water. I have heard of feven in one Mine, worked over each other. This power must have been attended with a complication of accidents and delays. However, foon after the above date, Mr. John Coftar, of Bristol, came into this county, and taught the natives an improvement in this machinery, by demolishing those petit engines, and fubftituting one large wheel of between thirty and forty feet diameter in their stead.

Hitherto we are all affured, that a large water wheel engine, if water is plenty and cheap, is most effectual and steady for the purpose of draining our Mines; but this power is limited; and beyond a certain gauge we dare not undertake. We know, that if we add to our power, we experience a lofs in time or motion, more than equivalent to the acquifition. Upon this principle we understand, that a thirty-eight feet wheel, or thereabout, is the best medium we can prefcribe to ourselves; pursuant to which we know, that, beyond a certain depth, we cannot fink with ease and conveniency to our intereft; and that another power becomes neceffary for our purpose.

It should seem as if we had been led by the kind hand of Providence in those discoveries; for as foon as we found out the ne plus ultra of the power of water, and the neceffity of

further

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further improvements in hydraulicks, a new and more fcientifick machinery prefented itfelf to the attention of the Miner. want of another piece of machinery, we had been ftinted to a certain depth, beyond which the fucceeding generation by the water wheel and bobs would be unable to fink. So that, happily for us and our pofterity, Mr. Newcomen's invention of the fteam fire engine, even in the weaknefs of its infancy, promifed that future excellence to which it is fince arrived, whereby we are enabled to fink our Mines to twice the depth we could formerly do by any other machinery.

Since the improvement of this machine's working itself, by opening and clofing the regulator and injection cock, moft other attempts have been very unfuccefsful. The vaft confumption of fuel in thofe engines, is an immenfe drawback upon the profits of our Mines. It is a known fact, that every fire engine of magnitude confumes to the amount of three thousand pounds worth of coal in every year. This heavy tax

upon Mining, in fome refpects, amounts to a prohibition. No wonder then, that we fhould be more defirous to leffen the expence of maintenance in thofe devouring automatons, than frugal in their erection. Many trials of mechanical skill have been made by our engineers, to very little purpose, for the total application of heat and the faving of fuel. The fire place has been diminished, and enlarged again; the flame has been carried round from the bottom of the boiler in a spiral direction, and conveyed through the body of the water in a tube (one, two, or three) before its arrival to the chimney; fome have ufed a double boiler, fo that fire might act in every pofiible point of contact; and fome have built a Moorstone boiler, heated by three tubes of flame paffing through it.

Indeed, the only improvement which has been made in the fire engine for thirty years paft, the publick will very juftly attribute to the fagacity of Mr. Watt, whofe fkill in pneumaticks, mechanicks, and hydraulicks, is evidenced by the powerful application of elaftick vapour, and by making a more perfect vacuum, nearly like that of the barometer, in his new conftructed fire engine.

But before I can explain Mr. Watt's engines, it is neceffary to premise a fhort account of the imperfections of the common fteam engines, and their caufes.

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