CHAINS WITH PRESSURErORGANS.
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Chains with Pressure-organs.
In the foregoing 'treatment of the simple chains we have repeat- edly had to consider the replacement of a rigid element by a pres- sure-organ, and in doing this have also examined the chains of which the pressure-organ became a part. The mono-kinetic properties of the pressure-organ have in all these cases shown themselves to be most important, and in the majority of cases force-closure has been necessary. If we wish to avoid this we come at once
into compound chains. Complete simple constrained closed chains containing pressure-organs do not appear to be possible. Such a simple chain, for example, as that shown in Fig. 420, which would be written
��FIG. 420.
�or in a contracted form (PVV } ~\ is essentially force-closed. If
the force-closure did not exist, for instance, the water would at once
��FJCJ. 421.
�leave the chamber. The arrangement has none the less its own
value, it is sin ply that of the common squirt.
If we arrange a second piston in the delivery pipe we obtain the arrangement of Fig. 421, already known to us. The chain has now four links instead of three ; it is, however, a compound chain for
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