31 $ 
for Preserving Corn on Ship -board, 
power capable of ventilating a cargo of 400 tons within 
the hour. But the air-vessel must be lengthened ; the 
pipes at the same time enlarged ; the metal of which the 
whole is constructed be in substance proportionable ; and 
the labour be that of a man, or perhaps two upon occa- 
sion. 
A ventilator, on the plan and dimensions here propo- 
sed, would come within the compass, I should think, of 
five or six guineas. One on the larger scale, caused by 
the increased substance of the metal, and the extra size 
and length of the pipes, might amount to twenty ; which , 
in either, is under fourpenee per quarter on the first car- 
go ; and as they will last many years if well painted., 
and, when not in use, taken to pieces and put carefully 
by, I flatter myself it is an experiment well worth trial ; 
particularly if a premium be offered to the ship-owner, 
who, by means of such machine, imports his corn pure 
and untainted from a distant land. 
Objections made to the supposed Effect of the Ventilator 9 
overruled , it is hoped , by the Considerations which fol- 
low them . 
First, The holes pierced in the tin tubes which are to 
lie under the corn, seem capable of issuing (especially if 
an effort be made upon them) a much larger quantity of 
air than the forcing-pump will supply in a given time. 
Consequently, a given quantity of these holes, under a 
given pressure, will be capable of issuing the whole sup- 
ply of air, without any assistance from the remainder. 
Secondly, If these positions are just, it must happen, 
that if a cargo of corn be unequally circumstanced in re- 
lation to its permeability, the whole of the air discharged 
by the pump will issue through the more permeable parts 
of it, without affecting, in any degree, the less permeable 
ones. 
Vol* i. nr 
