for preferving Corn on Ship-board. 395 @ 
leatheted on its upper furface, and faftened with an hinge of 
leather to the cylinder it is meant to clofe: affixed to its bot- 
tom is the fpindle G, paffing through a fpiral {pring H, which, 
being compreffed on the defcent of the valve, will, by its ela- 
fticity, caufe it to rife again, clofe the aperture above, and 
retain the air delivered beneath it. On connecting this cy- 
linder with the upper end of the nofle, at ee, Fig. 2, we muft 
carefully prevent any lapfe of air that way, by a bandage of 
oakum fmeared with wax, on which to ferew the cylinder, 
like the joints of a flute, air-tight. I is a bar of iron, having 
a rifing in its centre, wide enough for the fpindle to play 
through, but at the fame time fufficiently contracted to pre- 
vent the paffage of the fpiral fpring. 
Fig. 5. is an aflemblage of tin pipes, of any lengths, fhaped 
fuitably and conveniently to their fituation in the fhip, to the 
form of which, when fhut into one another, they muft be 
adapted ; obferving only, that the neck be ftraight for a 
length fufficient to admit the lower end of the cylinder, 
Fig. 4. as high as the letter F, or higher. 
Fig. 6. To the middle pipe, which runs along the bottom, 
fhould be fixed a perpendicular one, fully perforated, to con- 
vey the air more readily into the centre of the heap; and this 
may have a conical top, as reprefented in the plate, perforated 
with a f{maller punch to prevent the air from efcaping too 
haftily. In large cargoes, two or three of thefe perpendiculars 
may be neceffary; and each fhould be well fecured by an iron 
bar g, fcrewed down, to prevent their being injured by the 
fhifting of the cargo in ftormy weather or a rolling fea. The 
top of the conical cap of thefe pipes may reach two-thirds 
up the cargo. 
Fig. 7. is a valve of the fame conftruction as that repre- 
fented in Fig. 4, but inclofed in a tube of brafs, having a fe- 
male ferew at ff, adapted to the male ferew c¢, on the nofle 
Fig. 2, and may then be inferted into the head of the pipe 
Fig. 5. This will add to the expence; but, in a large appa- 
fatus, is to be preferred, as a more certain fecurity from lapfe 
of air, than the junétion of the tube Fig. 4, to the neck ee 
in Fig. 2. 
N.&, ce is a neck of wood, making a part of the bottom 
3E2 Fig. 2, 
