[ 58 ] 



C. is a valve well leathered on its top, and yield- 

 ing downwards to the preffure of the air when the 

 pifton is raifed up. 



D. is a crofs bar of iron to confine the valve, fo 

 that it may clofe inftantly on the return of the pifton 

 downwards. 



Fig. 4. Is a tin pipe or tube of lefs than four in- 

 ches diameter, and of fuch length as when fixed to 

 the bafe of cylinder fig. i , fliall admit the nofle d. 

 fig. 2, to within half an inch of the valve E. at the 

 bottom of the wooden cylinder F. in fig. 4, which 

 valve E. will then yield to the preffure of air con- 

 denfed in its pafiage through the nofle, and deliver 

 it into the pipes below. 



This valve mufl: be well leat;hered on its upper 

 furface, and faflened with an hinge of leather to the 

 cylinder it is meant to clofe ; affixed to its bottom 

 is the fpindle G. paffing through a fpiral fpring H. 

 which being comprelfed on the defcent of the valve 

 will, by its elafl;icity, caufe it to rife again, clofe 

 the aperture above, and retain the air delivered be- 

 neath it. 



On connecting this cylinder with the upper end 



of the nofle at e. e. we mufl carefully prevent any 



lapfe of air that way, by a bandage of oakum fmeared 



with wax, on which to fcrew the cylinder like the 



joints of a flute, air-tight. 



I. is a bar of iron, having a rifmg in its centre, 

 wide enough for the fpindle to play through, but at 



the 



