« Jor preferving Corn on Ship-board. 399 
Objeetions ee to the fuppofed Effee of the Ventilator, over- 
ruled, ut is hoped, by the Confiderations which follow them. 
Firtt, The holes pierced in the tin tubes which are to lie 
under the corn, feem capable of iffuing (efpecially if an effort 
be made upon them) a much larger quantity of air than the 
forcing-pamp will fupply in a given time. Confequently, a 
given quantity of thefe holes, under a given preffure, will 
be capable of iffuing the whole fupply of air, without ang 
affiftance from the remainder. 
Secondly, If thefe pofitions are juft, it muft happen, that 
if a cargo of corn be unequally circumftanced in relation to 
its permeability, the whole of the air difcharged by the pump 
will iffue through the more permeable parts of it, without 
affeGting, in any degree, the /e/s permeable ones. 
Thirdly, In cargoes heated in any degree, and in thofe 
infeed by that worm which faftens grains together by a 
web, the parts moft affected become niuch more clofe and 
denfely packed together than the reft, either by the fwelling 
of the heated grains, or by the web and dung of the worms 
which occupy the intervals between the grains. 
If fo, the parts of a cargo which require the moft yentila- 
tion will receive the leaft; but, im all cafes, it feems likely 
that the air difcharged will not regularly permeate the whole 
of the cargo, but will pafs through the parts where the grain 
lies lighteft, and leave untouched thofe parts wicre it is 
moft clofely packed together. 
Anfwer to the preceding Obje&tions. 
Though the holes appear numerous, they mutt be fmall, 
left the corn gain admiffion; and many (efpecially of the 
uppermoft) will be nearly, if not totally, topped by the pre!- 
fure of the grains upon them.. Befides, the pipes which 
convey the air towards’ the centre are not meant to be fo 
fully perforated as thofe at and beyond it; and all may be 
ftill lefs fo, if im practice found neceffary. But as the quan- 
tity of air delivered by the forcing-pump within five feconds 
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