Chap. XVII.

ON VALVES.

1185

hollowed out, to admit the cover G, to which a rod II is attached for opening andthe valve, working up and down through the cross bar E F.

Fig. 1818. is a pump used by Belidor to re- I

place the old one in a machine at the Pont !C : l l

Notre Dame, Paris ; its chief advantage is inthe valves, which offer less resistance to thepassage of the water; the valve, fig. 1820.,consists of a circular diaphragm movable on

shutting

Fig. 1817.

Fig. 1818.

gudgeons, whoseaxis does not passthrough the centre ;that is to say, thediameter being di-vided into twelveparts, A H com-prises seven, andIIB five. Thecentre, figs. 1825.,1821., 1822., of theaxis E F is also T ' 2part of the diameter,from the middle ofthe thickness of thediaphragm A B,which produces abent lever K I H,whose lesser arm,I K, corresponds tothe friction of thegudgeons, and theother I H sustainsat its extremity Hthe weight of thevalve, which canonly remain openwhen obliged bysomesuperior force.The unequal seg-ments of which thisvalve is composedare cut, fig. 1825.

Fig. 1819.

Fig. 1824.

Fig. 1821.

- ‘R

Fig. 1822.

Fig. 1825.

“ ,c cut, ug. 1023., A L, BM, in opposite directions, so that whenthe first, A L, which belongs to the greater segment, pressing downwards

4 G

is closedthe upper