The coals used in this engine is of as little value as the coals commonly burned on the mouths of the coal-pits are; for an engine of a three-inch bore, or thereabout, working the water up sixty feet high, requires a fire-place of not above twenty inches deep, and about fourteen or fifteen inches wide, which will occasion so small a consumption, that in a coal-pit it is of no account, as we have experienced. And in all parts of England, where there are mines, coals are so cheap, that the charge of them is not to be mentioned, when we consider the vast quantity of water raised by the inconsiderable value of the coals used and burnt in so small a furnace. What the quantity of coals used for one engine in a year is cannot easily be ascertained, because of the different nature of the several sorts of coals.
As for the cure of damps by this engine, the air perpetually crowding into the ash-hole and fire-place, as it is natural for it to do, and with a most impetuous force discharged with the smoke at the top of the chimney, the contiguous air is successively following it; so that not only all steams or vapours whatsoever, that may or can arise, must naturally force its way through the fire, and so be discharged at the top with the smoke, but this motion of the fire will occasion the fresh air to descend from above down all the pits, and every where else in the mine, but down the chimney; provided you have a heading drift, or passage from all the shafts or pits in the work, to that place where the engine stands; whether the mouth of the said pit and chimney be lower or higher than the mouths of any of the rest of the pits or shafts in the same work it matters not, for here will be a perpetual circulation of the air, and with that swiftness as is hardly to be believed. This I have tried and know to be true, so leave the ingenious miner to his own judgment, whether, when all the air is in a swift motion, that any stagnation of air (which has always been adjudged the cause of damps) can happen in any pit.
CHAPTER THIRD. THE MANNER OF FIXING THE ENGINE FOR WATER-MILLS, PALACES, AND GENTLEMEN'S SEATS, AND DRAINING FENS, AND SUPPLYING HOUSES WITH WATER IN GENERAL.
THE MANNER OF FIXING THE ENGINE FOR WATER-MILLS, PALACES, AND GENTLEMEN'S SEATS, AND DRAINING FENS, AND SUPPLYING HOUSES WITH WATER IN GENERAL.