406 Défeription of a Ventilator 
of time is equal to the contents of fixty * feet of four-inch 
pipe within the firft minute, the air (notwithftanding the 
manifold perforations, obftruéted as it is in meandering 
through a mafs fo nearly compacted as the bottom of the 
cargo muft neceflarily be by the preflure of the heap above) 
will undoubtedly reach to the end of the Pipes, and confe- 
quently affect the cargo even there. 
Be it farther obferved, that the flux of air Peg into 
an half-inch ftream, in its paflage through the nofle, to en- 
able it to overcome the refiftance of the fpiral {pring H, no 
fooner paffes the valve E, than it expands itfelf to the com- 
pafs of the pipe; by which expanfion, and extenfion (at the 
* Thus calculated: 
Inches. 
60 feet 4 
x 12 inches yet 
~ Produces 720 inches 16 the fquare of the diaméter of the 
as a multiplier. X 57854 pipe. 
== 12,5664 or area of the circle. é 
x 720 length of the pipe in inches. 
Which, divided by 231)9047,;8080(39,1679 gallons and decimal ‘parts, 
— the whole capacity 
2117 of 60 feet of pipe. 
3848 
221, XCe 
Then, a fingle difcharge of the forcing-pump being eight gallons, five 
fach difcharges amount to 4o gallons, which is more than equal to the 
contents of 6 feet of four-inch pipe. 
And as on the larger {cale of ventilators the pipes need not exceed the 
fame diameter, the power of the air injeéted, when its egrefs is ftopt, wilk 
increafe fufficiently to force its way through webs, mats, and other obftruc-. 
tions, though impervious to the atmofpheric fluid, unaflifted by fuch me- 
chanic aid. 
fame 
