_Author_. True, sir, I own that time out of mind there have been mountebanks and impostors in all faculties who pretend to great things, but do perform nothing effectually. And it would be hard if that should be drawn into consequence, that because some are knaves, therefore none are honest. I know the notions of the perpetual motion, or self-moving engine, and many such like whims are pretended to by designing men, and believed by ignorant ones: but the judicious man, who considers the laws of motion, knows it is an infallible rule, that whatsoever matter is to be removed upward, must have a force superior to the weight to be lifted up, if its motion be required as swift as the motion of the moving cause; if slower, proportionably less strength will do; if swifter, then the moving cause, as men’s hands, horses, or dead weight, then must the strength of the moving cause be increased proportionably, or no motion can be produced. And the experience of ages shows us this to be a most sure rule, allowing for friction, which is larger, the more wheels or parts an engine consisteth of; and, of consequence, the fewer parts or wheels an engine consisteth of the easier it works; so that by barely looking on a pump, if it has more parts or wheels than the common crank-work, you may conclude it worse; if a chain-work or tub-work the same. So that all that can be expected is, to make those go easier than they are now made to go by ingenious workmen expert in making them. And if you try how small a matter will move those engines when not loaded with water, you will find the friction so small as not worth any mending, could it be done, especially the tub-gin, whose friction increases the least in being loaded of any; but the others are vastly increased by the leathers of their suckers being forced broader, and rubbing with much greater force against the barrel they work in, according to the height the pipes are raised. And I hope, when it is considered how far this engine of mine differs from the bare pretensions of ignorant or designing men, and that any persons may see what my engine will perform before they contract for it, there will be found no ground for the least suspicion in any person concerned to employ them in mines; but, to the contrary, afford us a generous encouragement in a business so conducive to the increasing the mining trade, and thereby enrich themselves and the nation, and increase the king’s revenue. I could heartily wish all miners, for their own as well as their country’s interest, were good mechanics, and truly understood the nature, use, and application of all kinds of engines; for, I am sure, those that do will be my best friends, without expecting that horses, or men, or any other strength, can or will do more than what nature and the laws of motion has allowed them.