Ufe of Ventilators in Granaries and Mines. will be needful at first to tye a lighted candle at the end of a pole, and held it at the mouths of the trunks, thereby to make fome estimate of the quantity of foul air that is drawn into the feveral trunks. And when the upper floors are ventilating, the air is hindred from being drawn out of the lower floors, either by fhutting all their trunks, or by a fliding iron, which fhuts the A defcending trunk, near the floor of the low eft of the rooms that are ventilated. But when the wards of the lower floors are to be ventilated, then all the fide branching trunks of the upper floors are to be shut, that the whole effect of ventilation may be in the wards of the lower floors. By this means, all the wards may be venti- B lated in their turns, in fuch proportion as shall by experience be found moft convenient. All thefe fliding fhutters have large figures, viz. 1, 2, 3, &c. painted on them; that by thefe numbers they may more easily be defcribed, and referred to, in the feveral directions for ventilating the feveral wards. In the cafe of a prison that is built with an open area or court in the middle; in this cafe, the fide of the prifon which is oppofite to the fide, where the ventilators are, may commodiously be ventilated in its turn, by having a round brick air gutter under ground, through which the foul air of those wards may easily be drawn. In leffer prifons the ventilators need be but one half of these in Newgate, which may easily be worked by men; as is found by experience in feveral prifons and hospitals. The like ventilators, to be worked either by a wind or water mill, will be of great ufe to preferve great quantities of corn in granaries. This, M. du Hamel de Monceau, Member of the Royal Academy of Sciences, has, on my propofal of it to him, actually put in practice, by fixing a windmill on a publick granary which works large ventilators, that convey And where plenty of air up through the corn. it can be had, a water mill would be much the beft, because it could work conftantly during the whole day; by which means a vaft quantity of corn of any depth might be preserved in one granary, and that with no great expence ia building it. C D the fire engine which draws the water out of fome mines, or, where neither of these conveniences can be had, then by a windmill, which as it would be becalmed about one fourth of the year, during thofe times by a horse. The Imall ventilators, fig. 6, in the ventilator book, would be of great ufe to make the air of an air-fhaft wholfome, while digging;. and to blow away the fumes of gunpowder immediately when a rock is blown up with it. And this may be done by letting down a trunk about four inches wide into the fhaft, with a trunk of canvas at its lower end, which will readily comply to go lower and lower, as the shaft is dug deeper. And whereas in fome lead &c. mines, the large mine is pretty healthy, by having a progreffive motion in the air; but yet the fide branching mines unhealthy, for want of fuch a current or, motion in the air in this cafe, the small ventilator, fig. 6, might be of fervice, if placed not far from the mouth of the branching mine; there to blow into it the lefs impure air of the main mine. : It is well known, by long and too frequent experience, that the destructive goal diftemper is occafioned by the bad air in prifons, which is filled with the great quantity of vapours that arise from the breath and perfpiration of the prifoners; which being, as Dr Keil found it here in England, at the rate of 39 ounces, in 24 hours, from one perfon, this in 100 prifoners will amount to 243 pounds. Now fuch close confined air, by long ftagnating is very apt to putrefy; and putrefaction being the moft fublime and powerful diffolvent in nature, it diffolves the blood and humors of human bodies, and thereby produces that very infectious, peftilential difeafe, which is called the goal diftemper. And fuch clofe-confined, E damp, putrid air will not only diffolve human bodies, which are framed of materials ftrongly tending to putrefaction, but also even heart of oak, as is well known by daily experience every where. The undoubted benefit of thus ventilating prifons is very evident by the following expeFriment, viz. At my defire, Dr Langrish, a phyfician at Winchefter, burnt a candle of fix to the pound in the dungeon of that prifon, in the morning, before doors or fhutters had been opened; where it wafted in half an hour 66 grains, candle had wafted 88 gr. in burning as long in a good air. And after the dungeon had been well ventilated with ventilators for half an hour, the prifoners remaining there all the while, the fame candle wafted in another half hour 87 grains, that is very nearly as much as in a good air at firft; which fufficiently fhows the great ufefulness of ventilators, in prifons, fhips and hofpitals; for as a candle burns more or less vigorously in proportion to the degrees of purity or impurity of the air, fo is our vital lamp proportionably either enlivened, or incommoded, or totally quenched, according to the different degrees of purity or impurity of the air which we breathe. The air might be conveyed thro' small trunks about 4 inches fquare, layed on the floor of the granary at the diftance of about four feet from each other. The four joynts or feams of the trunks to be about one tenth of G an inch wide, for the air to pass thro' their whole length. Thefe trunks to be fupplied with air from the ventilators thro' a larger trunk layed across them, either at one end, or in the middle of the granaries, according to the largeness or fmallhefs of the granary. This has been found by experience a cheap and good method. Mines might be made very wholfome by means of large ventilators, to convey plenty of H air through trunks to the fartheft parts of them. They might be worked either by a stream in the mine or on the furface of the earth; or, as Mr Erafmus King very rightly propofes, by [GENT. MAG. April, 1752.] The doctor obferved that at the firft going down into the dungeon the air affected the mouth and throat with a remarkable fatnes, but not A a |