Author . No: they cannot fail me; because experience shows us, that brass valves improve, rather than grow worse, by twenty or thirty years use in any force-work, where constantly worked, and where they rise and fall twenty times oftener than my valves will do.
Miner . But what think you, sir, if you should meet with such corrosive water in some of our mines, as will, in a little time, eat through your copper vessels.
Author . Truly, sir, this question does a little startle me, because I never expected to meet any water of such a corrosive quality in any mine: and could I find out a mine, whose water abounds with such acid particles, as to destroy or injure the copper vessels of my engine, I would drain that mine for nothing but the water I shall take up; because the water would be more valuable than any ore (I believe) in England. And were there even a tenth part of aquafortis to nine-tenths of common water, which is impossible to suppose it should be, I say, such a water could have no effect on the coppers, were that water to lodge some time in the copper vessels, much less in passing through them with that celerity and rapid motion that always accompanies it.
Miner . But, sir, will not such a continual fire, as must be kept under your boilers, burn them out in two or three months’ time, and spoil the work of your engine?
Author . I can assure you they will not decay in some years, unless some fellow be hired or employed on purpose to do it. And should any villain be employed to burn, break, or destroy any of the engines now used in your works for raising of water, we are then on the same level with you in that point. But I will give you one reason why my engines will not easily decay, and I am sure that will go further with you than all the affirmation I can make. For, first of all, although a white heat will melt copper, and a red heat, and sudden cooling it again, will scale the copper, yet such a heat as is possible for it to have or suffer while water is in the boiler can have no ill effect, or cause any alteration in our copper. A friend of mine has coppers used in sugar boiling of twenty years’ standing. They may be a small matter worn with cleaning on the inside, whereas on the outside there does not appear the least visible decay: for as soon as the fire has thrown a thin coat of soot on the outside of the boiler, the flame has no other effect on it than to cause the water in it to boil.
Miner . But we have often combustible vapours in our mines, which taking fire from the candles used there, do, by a sudden explosion, destroy both the mine and the miner; and therefore I am afraid that the fire used in your engine will be very dangerous, and apt to kindle those combustibles more than our candles.
Author . To answer this objection, I will desire leave to give you my notion of those combustibles, which, in short, is this: that when your miners come into a close place, where there is no circulation of air to carry off the effluvia, or atoms constantly rising like fine dust in a powder-mill, they by knocking and working do increase to be very numerous, like to those loose particles in a powder-mill. But it is the work of some time for those vapours to come to perfection; for I have heard several experienced miners say, that it is common to avoid the danger of those vapours, by retiring as soon as they see the flame of their candles burn longer than ordinary, which may be, discerned sometimes long before the air is thick enough of this combustible matter to take fire at once, and, like gunpowder, to destroy all. I did hear one say, that from an inch and a half, once the flame of his candle did gradually increase to two feet long, and yet he escaped. Which makes it very plain, that stagnation of air is the sole cause of this inconvenience in mines, which may be totally prevented by a pipe going from the ash-pit of our furnace to any part of the mine liable to stagnation. For the air will press with great violence through the pipe into the fire, before the combustible matter can be ready to do any hurt, and passing through the fire, make way for fresh air to descend in the room of it. So that our fire, instead of blowing up of your works, is the best means that can be used to prevent so fatal an accident; and will likewise carry off all unwholesome vapours, damps, or steams, which may proceed from corruption of air, by stagnations or vapours arising from any poisonous earth or mineral.
Miner . This notion of yours carries reason and demonstration along with it, which pleases me wonderfully. But, sir, is not your price too great for these engines of yours?
Author . By what I shall offer to you, as to my price, I am sure to have you a friend to me and my engine for ever. For I must tell you, that I would never have sent my engine into the world, if it would not raise your water with more ease and conveniency to you and your servants, and also much cheaper than any other engine ever used in your works, without which I could never propose any advantage to myself by it. And to convince you of the truth of my assertion, I dare undertake the engine shall raise you as much water for eightpence, as will cost you a shilling to raise the like with your old engines in coal-pits. By this one article the miner will save one-third part of his former charge, which is thirty-three pounds six shillings and eightpence saved out of every hundred pounds. A brave estate gained in one year out of such great works, where three, six, or it may be eight thousand pounds per annum is expended for clearing their mines of water only, besides the charge and repair of gins, engines, horses, &c. I hope you will not now account my engines dear under such conditions as I now offer; but if I should, with you, suppose my engine proportionably dear, or as dear as the engines you now use for drawing up your water, which is impossible, my engine will be preferable before yours in many respects, insomuch, as mine prevents your damps, and the evil effect of them: and as it will be my interest to allow those that first set my engine at work considerable advantages, so I hope I may assure myself of due encouragement from the ingenious, who are ever studious to promote all inventions useful and beneficial to the public; for they must conclude, that an engine which for some time has daily employed the best artificers to work on it, was not to be brought forth in one day: and to bring it to that perfection you now find it, must have cost me and my friends not a little money to make the workmen capable of their work with that certainty and exactness they now do. And for working the engine any person may have his servant taught it, it being to be learnt in a very short time by one of an ordinary capacity.
Miner . But there are people who pretend to do great things in the improvement of engines to work by hand or horses, the hope and expectation of which has hindered some of us in our work and tired others, so as to make them out of love with all engines, and almost with the trade of mining. And though I wish the contrary, I fear this may prove some hinderance to the promoting your interest.