VOL. Xtll.] PHILOSOPHICAL TRANSACTIONS. 553 



June 6, 8, and 11, the same. 



July 3, and 23, very loud and long, and shook the houses. — Also March 

 19, 1729. — Sept. 8, and 29, the same. And the same in the months of 

 October and November. 



Similar shocks and noises were also in most of the months of the following 

 years 1730, 1731, 1732, 1733, 1734, 1736, 1737, 1739, 1740, 1741. 



An Account of Mr. Sutton's Invention and Method of Changing the Air in the 

 Hold, and other close Parts of a Ship. By Ricliard Mead, M.D., F.R.S. 

 N° 462, p. 42. 



It is found by daily experience, that air shut up and confined in a close place, 

 without a succession and fresh supply of it, becomes unwholesome, and unfit 

 for the use of life. This is more sensibly so, when any stagnating water is pent 

 up with it. But it becomes still worse, when such air is used in respiration, 

 that is, becomes moister and hotter, by passing and repassing through the 

 lungs. 



These bad effects, in different degrees, according to the different manner in 

 which air is inclosed, are observed in many cases; particularly in deep wells and 

 caverns of the earth, in prisons or close houses, where people are shut up with 

 heat and nastiness : but most of all in large ships, in which, with the stench of 

 water in the hold, many men being crouded up in close quarters, all the men- 

 tioned circumstances concur in producing greater mischief than would follow 

 from any of them singly. 



The reason of these bad effects. Dr. Mead thinks, is partly by the air losing 

 its elasticity in such circumstances, and partly by being impregnated with noxi- 

 ous effluvia,* either from unwholesome substances of any kind, or from the in- 

 fectious breath of diseased bodies ; hence it will become quite poisonous and 

 deadly. It is proposed at present to find out a remedy for this evil in ships 

 only: but by making alterations according as particular places require, the same 

 may be applied to any houses or parts of them, as prisons, the sick wards in 

 hospitals, &c. 



Now it is a natural consequent of the elasticity of the air, that when it is 

 rarefied in any part, (which is most effectually done by heat) the neighbouring 

 air will rush that way, till this part is brought to be of an equal density and 

 elasticity with itself; and this again will be followed by the air next to it: so 



* Air under the circumstances abovementioned becomes unfit for being respired, not only in con- 

 •equence of being loaded with noxious effluvia, [and with carbonic acid gas] but also in consequence 

 of the abstraction of a portion of its oxygen, which is absorbed by the blood during the respiratory 

 action. 



VOL. VIII. 4 B 



