' C 63 ] 



remainder of the hour being employed in the like 

 ventilation, five tons of frelh air would pafs above 

 tvsrenty times repeatedly amidil the grains to cool, 

 refrefh, and fweeten the cargo. A purification thus 

 adminiftercd once in eight-and-forty hours, would, 

 1 conceive, be amply fufficient to preferve the corn 

 from taint or injury be the voyage ever fo tedious, 

 and unlefs it fliould by negleft have over-heated and 

 grown together or fettled too clofe, the labour would 

 be that of a boy only, for the dairy-girl at her churn 

 works harder than he otherwife need to do at this. 



My air-veflel is, for the fake of cheapnefs, con- 

 fined to the narrow diameter of i o inches ; but as 

 the contents of circles are proportionate to the 

 fquare of their diameters, by enlarging that you 

 increafe their power accordingly. Wherefore, by 

 extending their diameter to 14 inches, the contents 

 will be nearly doubled, and by adding 10 inches 

 more to the length of the ftroke, you alraofl treble 

 the difcharge of No. i, and obtain a power capable 

 of ventilating a cargo of 400 tons within the hour. 

 But the air-veflel mufl be lengthened, the pipes at 

 the fame time enlarged, the metal of which the whole 

 is conftrufted be in fubflance proportionable, and 

 the labour that of a man, or perhaps two upon oc- 

 caGon. 



A ventilator on the plan and dimenfions here pro- 

 pofed, would come within the compafs, I fliould 



think. 



