562 ' PHILOSOPHICAL TRANSACTIONS. [aNNO 1742. 



air, yet unless, by openings properly adapted, the air be suffered to pass freely 

 through, the external air proves as a stopple to the internal, and only mixes 

 with the next in contact; as is evident from the common occurrence in privies, 

 which are scarcely offensive in clear weather, but are much so in foul or windy, 

 from a diminution of the incumbent pressure, when the vapours that have been 

 pent up, expand to a considerable distance. 



To prevent the above-mentioned inconveniencies, and preserve the health 

 and lives of that valuable part of the nation, the seafaring people, many schemes 

 have been thought of; particularly the machines of those two very worthy inge- 

 nious and industrious members of this Society, the Rev. Dr. Hales and the Rev. 

 Dr. Desaguliers; the first by an instrument which he calls the ship's lungs, in 

 his treatise on Ventilators, and the latter by a machine, which is an improve- 

 ment of the Hessian bellows, Philos. Trans. N° 437 ; but as these have been 

 laid before the Society by the gentlemen themselves, Mr. W. passes them over, 

 and proceeds to mention the contrivance commonly made use of, viz. the 

 wind-sails. 



These are made of the common sail-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 obtusely. When they are made use of, they are hoisted by ropes to about 

 two- thirds or more of their height, with their basis distended circularly by 

 hoops, and their apex hanging downwards in the hatch-ways of the ship; above 

 each of these, one of the common sails is so disposed, that the greatest part 

 of the air, rushing against it, is directed into the wind-sail, and conveyed, as 

 through a funnel, into the upper parts of the body of the ship. 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 sanction to this device, 

 it is subject to many inconveniencies: 1st, Each ship having commonly three 

 of these, one to each mast, the seamen are a considerable time in getting their 

 apparatus ready, and hoisting them up, to make use of. 2dly, They can only 

 be used in mild weather. 3dly, Near the equator, where fresh air is most 

 wanted, there sometimes happen such dead calms, that they are useless, by not 

 having air enough to distend them. 4thly, The air thus admitted passes only 

 into the upper and more open parts of the ship, so that the well, &c. receive 

 no change from it ; and it is observed, that sometimes, on using them after 

 some discontinuance, they drive offensive air into the cabin, and more airy parts 

 of the ship, like as the pouring some fresh into stinking water makes more 

 water stink, though in a less degree. 5thly, They are improper to be used in 

 the night-time, when the people are sleeping between decks. And, lastly, ad- 

 mitting they had none of the former inconveniencies, their use must be destruc- 



