SI 4 
Descript ion of a Ventilator 
Thirdly, In cargoes heated in any degree, and in those 
infected by that worm which fastens grains together by 
a web, the parts most affected become much more close 
and densely packed together than the rest, either by the 
swelling of the heated grains, or by the web and dung 
of the worms which occupy the intervals between the 
grains. 
If so, the parts of a cargo which require the most ven- 
tilation will receive the least ; but, in all cases, it seems 
likely that the air discharged will not regularly permeate 
the whole of the cargo, but will pass through the parts 
where the grain lies lightest, and leave untouched those 
parts where it is most closely packed together. 
Answer to the preceding Objections . 
Though the holes appear numerous, they must be 
small, lest the corn gain admission ; and many (especially 
of the uppermost) will be nearly, if not totally, stopped 
by the pressure of the grains upon them. Besides, the 
pipes which convey the air towards the centre are not 
meant to be so fully perforated as those at and beyond it; 
and all may be still less so, if in practice found necessary. 
But as the quantity of air delivered by the forcing-pump 
within five seconds of time is equal to the contents of 
sixty * feet of four-inch pipe within the first minute,, the 
* Thus calculated i 
Inches. 
60 feet 4 
X 1 2 inches X 4 
Produces 720 inches 16 the square of the diameter of the 
as a multiplier. x ,7854 pipe. 
HI 12,5664 or area of the circle. 
X 720 length of the pipe in inches. 
Which, divided by 23 1)9047, 8080 (it 39, 1679 gallons and decimal 
parts, the whole capacity of 60 feet of pipe. 
