VENTILATOR. 



between decks, is far from being fufficient for that piirpofe ; 

 nor can it be ufed with equal fafety to the fick, and thofe 

 who are fleeping, by means of the ftrength of the wind, 

 which conveys the air with too much violence. But wlien 

 the foul air is carried off by means of ventilators, not- 

 withftanding the great velocity with which they throw out 

 the air, vi'hich they may do at the rate of fixty tuns in a 

 minute, yet the motion of it downwards into the hold, to 

 fupply what was carried off, is fo very gentle that it cannot 

 be perceived ; becaufe the fum of all the open pafTages for 

 it through the deck exceeds the opening of the trunk of 

 the ventilator, in fo great a proportion as lOO to i, or more. 

 Befides, in a calm, the wind-fail can do little or no good : 

 nor when the ftiip is under fail, at which time the wind- 

 fail is not ufed. And it is to be obferved, that it is not 

 the ventilating of a fhip now and then with a wind-fail, 

 when wind and weather ferve, that will fuffice ; it ought 

 be done daily, if due regard be had to the health of the 

 ibip's crew. The great quantity of rancid noxious vapours, 

 which are incelTantly exhaling from a number of living hu- 

 man bodies, the ftench that inceflantly arifes from the bilge- 

 water, and from the hot, ftagnant, putrid air in the hold, 

 makes it very advifable to refrefh fo bad an air continually, 

 either with the wind-fail, when that can be properly ufed, 

 or elfe with ventilators, which are intended to fupply the 

 defedts of the wind-fail. 



Ventilators muft alfo be of particular fervice in new 

 fhips, which are obferved to be more unhealthy, on account 

 of a greater quantity of fappy wreak which arifes from 

 new timber, and makes the confined air the more un- 

 wholefome. 



They will alfo be an effeftual prefervative of horfes in 

 tranfports, where they are fometimcs fufFocated, when in a 

 ftorm there is a neceflity to fhut the hatches down. 



Thefe ventilators will alfo drive out of the hold of a 

 (hip that dangerous vapour which arifes from corn, which 

 is fo noxious, that fometimes they dare not venture into 

 the hold, till after the hatches have been opened for fome 

 time. 



Ventilation will not only be of fervice to preferve feveral 

 kinds of goods, but alfo the timbers and planks of the 

 hold itfelf, when laid up in ordinary, as well as when in 

 ufe, and will make the air in the hold lefs noxious, though it 

 will ftill be offenfive to the fmell, by reafon of the bilge -water. 

 But this may be made lefs offenfive, by often letting in fweet 

 water from the fea, and then pumping it out ; which good 

 praftice ought to be continued, notwithftanding the ufe of 

 the ventilators. 



What is here faid of the foul air of fhips may be ap- 

 plied to that of mines, gaols, workhoufes, barracks, and 

 hofpitals. In mines, ventilators may guard againfl the 

 fuffocations, and other terrible accidents arifuig from damps ; 

 which fee. (See alfo Ventilation.) The air of gaols 

 has been often known to be infeftious ; and we had a 

 fatal proof of this, by the accident that happened fome 

 years ago at the feffions at the Old Bailey. To guard 

 againft the like for the future, as well as to preferve the 

 health of the prifoners, a worthy magiflrate, in 1752, had 

 ventilators placed in Newgate, which were wrought by a 

 windmill; and in the beginning of the year 1753, Dr. 

 Hales gave an account of the good fuccels attending the 

 ufe of thefe machines, by a remarkable decreafe in the 

 ufual mortality and ficknefs of that place. 



Although the old prifon at Newgate is now taken down, 

 and a much more commodious one erefted near the fame 

 fpot, it may not be improper to give a brief account of 



the manner in which the ventilators of Dr. Hales were con- 

 flrudled, and how they were moved by the windmill an- 

 nexed to them. The midriffs h, h, (Jig. 4.) of thefe two 

 ventilators, two pair of which were laid upon one another, 

 were each nine feet long, and four and a half wide, and 

 moved up and down by the flat iron rods e,f, palfing through 

 the lower and upper ventilators, and through an iron plate 

 at z, about three inches fquare ; over which is another 

 broader iron plate, with a wide hole in its middle, to give 

 room for the iron rod at g to move fideways to and fro, 

 with the under plate, the hole of which exaftlv fits the 

 iron rod, fo that no air can efcape at g ; and there are the 

 hke plates at i, the top of the ventilator ; and at /, g, 

 are joints, where the iron rods are fixed to the midriffs, by 

 which means both are moved up and down at the fame 

 time ; and the iron rods of both fides of the ventilators 

 being fixed to one common lever at e e, all the four mid- 

 riffs are thereby alternately worked up and down at the 

 fame time. The valve-holes -v, v, x, x, &c. are twenty -three 

 inches long, and fix and a half wide, covered with buck- 

 ram glued on them, and move on lifts of tanned fheep-fltin, 

 and fall on lifts of woollen cloth nailed round the valve -holes. 

 A very large note [Jig- 5.) is fixed with iron hooks k, k, to 

 the ventilators /, / ; and this nofe is divided into three fpaces, 

 the middle and largeft of which, m m, receives all the foul 

 air blown into it from the eight middle valves x, x, x, x, 

 [Jig- 4.), whence it paffed through a trunk t t, fixteen 

 inches wide, through the leads of the prifon, into the open 

 air ; the top of this trunk being covered with weather- 

 boards to keep the rain out, and the middle valves hanging 

 fo as to open outwards. The two other outer fpaces of 

 the nok p p, receive the foul air, drawn into them, from the 

 feveral wards, through the trunks j>, p, and paffing off into 

 the ventilators, through the eight outer valve-holes i>, v, v, v, 

 whofe valves open inwards. In thefe outer partitions of 

 the nofe there are two holes z, ni, [Jig. y. ) covered with 

 boxes, in the bottom of each of which there is a large 

 moveable valve, opening upwards, and towards the ventila- 

 tors : thefe are made of fuch a weight, as to open only 

 when all the trunks to the feveral wards are fhut : by which 

 the ventilators will always be fupplied with air, fo as not to 

 endanger the breaking of the midriffs for want of it. 

 Thefe ventilators, about eighteen inches deep in the clear, 

 were fixed in an upper room of Newgate, in order to be 

 near the windmill on the leads, which worked them. From 

 each of the outer noftrils there went a trunk, twelve inches 

 in the clear withinfide ; and from thefe trunks, which de- 

 fcended through all the floors as far as a little below the 

 ceiling of the ground rooms, leffer trunks, fix inches fquare 

 within, branched off, near the celling of every room ; and 

 extended more or lefs into the feveral wards, fo that when 

 the foul air was drawn out of any ward, the frefli air 

 might enter on the oppofite fide, and drive out all the foul 

 air before it. By other contrivances with fliduicr fliutters 

 and handles, the feveral wards might be ventilated at fuch 

 a time, or in fuch' a degree, as was found neceflary. In 

 the cafe of a prifon that is built with an open area in the 

 middle. Dr. Hales obferves, that the fide of the prifon 

 which is oppofite to the fide where the ventilators are, may 

 be commodioully ventilated in its turn, by having a round 

 brick air-gutter under ground ; througli which the foul air 

 of thofe wards might eafily be drawn. 



The windmill for working the ventilators was contrived 

 to move with a fmall degree of wind, and to obtain a fufd- 

 ciejit power in a fmall compafs. In Jig. 6, c is one of the 

 crofs-trees which fupport the mill-poft d, and the braces e,e; 



the 



