_Miner_. You have, sir, hitherto given me undeniable answers to my former objections, for which I thank you; but I fancy I shall puzzle you, when I ask you how you will manage your engine to draw up our water, where the shafts are not direct, but turn and wind to and fro? _Author_. Sir, this last question is so far from being any hardship put upon my engine, that no engine ever yet invented was so naturally adapted to work in these crooked shafts as mine is; for let the windings or turnings of the shafts be what they will, the perpendicular weight of water is all that my engine has to account for, and is the same as if it made the figure of a distiller’s worm, and went through the straightest pipe imaginable, except a little inconsiderable friction of the water against the side of the pipe that is crooked, more than is in the straight pipe, which is so small a matter, that a very nice judge would hardly be able to distinguish whether the crooked or straight pipe carried off most water in the working. For the flue that carries the smoke, experience sufficiently instructs you, that you may turn and wind it any way you please, and that such windings in their drawing most air do rather improve than prejudice your flue, as any one experienced in building of furnaces can inform you. _Miner_. Well, sir, I find that our crooked shafts will not any way incommode your engine: but what think you of accommodating your engine to the service of the lead mines, whose shafts are many times so narrow, that it will be very difficult to get your engine down? _Author_. I perceive, sir, you are yet much a stranger to the nature of my engine, which is so furnished with brass screws, and as strong as the very metal itself, that you may take it to pieces, and with ease put it together again fit to work in a few hours’ time; and so contrived, that where a man can well go down, there I can put down my engine in several pieces and fix them below, for the greatest boiler belonging to my engine is between twenty-four and thirty inches diameter, and may, if occasion require, be made yet much narrower and deeper. And that if it be difficult to bring the shaft of the mine to fit my engine, I can, with much ease, make my engine to fit the shaft of any mine. _Miner_. But will not these brass valves that you speak of in your engine, speedily wear out and stop your work? _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.