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MARTIN

FOLKES, Esq;

President of the Royal Society.

SIR,

A Cording to my promile, I have herewith fent

chine, which I drew up fome time since, and intended to lay before the royal society in December last, before I knew either that a model would be shewn by Mr Sutton, or that Dr Mead would have presented his account thereof. I am conscious of the disadvantages my slender performance must appear under after the reading of one upon the fame fubject from fo celebrated

pen as Dr Mead's. These remarks were the result of several times seeing the machine, when first put in execution at Deptford. I hope it will not take up too much of the society's time to read my paper this evening, and am, SIR,

Your most obedient humble servant,
Aldersgate-ftreet,
Thursday morning,

W. WATSON. April 1. 1742.

Some 225

Some observations upon Mr Sutton's inven

tion to extract the foul and stinking air from the well and other parts of ships, with critical remarks upon the use of wind-fails, by William Watson, F. R. S.

London, Dec. 4. 1741.

Read April 1. 1742.

A

S nothing is more conducive to the health of the

human body, than the taking a sufficient quantity of wholesome air into the lungs ; so the contrary is attended with pernicious, and often with destructive confequences.

One of the great uses of air in inspiration is to cool the blood passing through the lungs, where nature has provided, according to the excellent Malpighius, that the blood should be distributed through a vast number of exceedingly fine arteries, which occupy the thin vesicles of the lungs ; and by this means the blood is exposed to the air under a prodigiously large surface, whereby the putrefaction is prevented, which, from the alcacescent quality of that Auid, would otherwise be fpeedily destructive.

Observations inform us, that contagious distempers are more frequent in hot climates than in cold ; and in closely-built cities full inhabited, than in towns : the former may, in some measure, proceed from the too great heat of the air, not fully anfwering the above-mentioned purposes ; and the latter from too VOL. II.

many

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many people breathing in the same atmosphere, thereby rendering it unfit for respiration.

It has been frequently tried, that if a gallon of air be contained in a bladder, and, by means of a blowpipe, inspired and expired into the lungs of a man, without having any communication with the external air ; in the space of a minute, or little more, it becomes heated, and unfit for respiration ; and without the addition of fresh air, the person making the experiment would fpeedily be suffocated. The divingbell is another instance of the fame kind, wherein a constant fupply of fresh air must be had, to keep out the water, and refresi the people included.

Although air is absolutely necessary to our exiftence, and necessity constrains us inevitably to breathe therein, it may be made a vehicle of most malignant poisons, as witness the famous Grotto del Cani in Italy, the poisoning air by charcoal, and air impregnated with the fumes of fermenting vegetable liquors. Stagnant air, either alone or mixed with water, foon becomes very offensive and pernicious; as in wells dug for the fupply of water, and disused for fome time ; as is the air also in the wells and in the holds of ships, which is occasioned principally by what is usually called the bulge-water, which, if the fhip is tight, and not frequently pumped, becomes not only very offensive, but fo extremely poisonous, as frequently to suffocate those feamen, who, as the pumps are subject to be clogged with filth, venture down to cleanse them; and will cause also in persons at a distance violent head-achs, cold sweats, and frequent vomitings, which continue more or less, in proportion to the distance from the well of the ship,

when

when the injury was received, and the degree of putrefaction in the water and air.

The air, in fhips particularly, is very liable to be vitiated, not only from the bulge-water, but from too many people breathing in the fame atmosphere; especially in ships of war, hospital-ships, and those used in the Guinea trade for negroes; where a number of uncleanly people, being stowed too close together, heat the air, make it replete with noxious effluvia, destroy the particles therein adapted to cool the lungs, particularly the acid nitrous gas. This principle is abundant in cool air, and manifests itfelf not only from the quantity of nitrous crystallizations, which may

be collected from caverns of the earth, especially those open to a northerly aspect, but also from exposing pieces of the flesh of animals fresh cut, or their blood, whereby the colours of their surfaces are foon changed from a dark deep red to a more lively and florid one. Air robbed of this valuable property, and replete with hurtful ones, not only from the people, but from the stinking water in the well and lower parts of the skip, must produce the most putrid, if not pestilential fevers.

Although the æquilibrium within places confined is maintained by the external air, yet unless, by openings properly adapted, the air is fuffered to pass freely enough, the external air proves as a stopple to the internal, and only mixes with that portion of it which is next in contact : this is evident from the common occurrence in privies, which are scarcely offensive in clear weather, but are much fo in foul or windy, from a diminution of the incumbent pressure of the

atmosphere,

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atmosphere, when the vapours that have been pent up, expand themselves to a confiderable distance.

To prevent the above-mentioned inconveniencies, and to preserve the healths and lives of the feamen, that valuable part of the nation, many schemes have been thought of; particularly the machines of those two very worthy, ingenious, and industrious members of this society, the Rev. Dr Hales, and the Rev. Dr Defaguliers; the first by an instrument which he calls the ship's lungs *, and the latter by a machine t, which is an improvement of the Hessian bellows ; but as these have been laid before the society by the gentlemen themselves, I fhall pass them over, and proceed to mention the contrivance commonly made use of, I mean the wind-fails. They are made of the common fail-cloth, and are usually between 25 and 30 feet long, according to the size of the ship, and are of the form of a cone ending obtufely; when they are made use of, they are hoisted by ropes tò about two thirds or more of their beight, with their basis distended circularly by hoops, and their apex hanging downwards in the hatchways of the ship; above each of these, one of the common fails is so disposed, that the greatest part of the air, rushing against it, is directed into the wind fail, and conveyed, as through a funnel, into the upper parts of the body of the thip. These must be hung up and taken down every time they are used, and the supply by this method is not constant. Though custom has given a fanction to this device, it is fubject to many inconveniencies. It, Each ship having commonly

* See Dr Hales's treatise of ventilators, Philof. Trans. No 437

three

+ See

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