m 
for preserving Corn on Ship-board . 
This valve must be well leathered on its upper surface* 
and fastened with an hinge of leather to the cylinder it 
is meant to close : affixed to its bottom is the spindle G> 
passing through a spiral spring H, which, being com- 
pressed on the descent of the valve, will, by its elastici- 
ty, cause it to rise again, close the aperture above, and 
retain the air delivered beneath it. On connecting this 
cylinder with the upper end of the nosle, at e e , Fig. 2, 
we must carefully prevent any lapse of air that way, by 
a bandage of oakum smeared with wax, on which to 
screw the cylinder, like the joints of a flute, air-tight. I 
is a bar of iron, having a rising in its centre, wide enough 
for the spindle to play through, but at the same time 
sufficiently contracted to prevent the passage of the spi- 
ral spring. 
Fig. 5, is an assemblage of tin pipes, of any lengths, 
shaped suitably and conveniently to their situation in the 
ship, to the form of which, when shut into one another, 
they must be adapted ; observing only, that the neck be 
straight for a length sufficient 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 bot- 
tom, should be fixed a perpendicular one, fully perfora- 
ted, to convey the air more readily into the centre of the 
heap ; and this may have a conical top, as represented in 
the plate, perforated with a smaller punch to prevent the 
air from escaping too hastily. In large cargoes, two or 
three of these perpendiculars may be necessary; and 
each should be well secured by an iron bar g , screwed 
down, to prevent their being injured by the shifting of the 
cargo in stormy weather or a rolling sea. The top of the 
conical cap of these pipes may reach two-thirds up the 
cargo. 
Fig. 7? is a valve of the same construction as that re- 
presented in Fig. 4, but inclosed in a tube of brass, having 
