7. 
316 Improved Piston for Steam- Engines. 
the tube so, or the orifice 0, be small, there will be no oc* 
casion for the valve s. Now it is plain from the figure, if 
the back be filled until the surface of the water rises to x7, 
the float 7 will be lifted, and the valve x brought within the 
reach of the tube so when it descends, which will presently 
be the case; for when the surface arrives at v it will run 
through ik into H, and cause it to descend and shut off the 
cock F. The wheel T should be a little flatted near y, that 
after being set in motion it may not be stopped by friction 
until the cock is effectually turned off, 
XLIX. Description of Mr. Antuur Woour’s improved 
Piston for Steam- Engines. 
Tas common method of packing the piston of a steam- 
engine is so well known, that a very particular description 
of it in this place is not necessary. Suffice it to say, that 
the hollow part round the piston (A,a, Plate VII.) is filled 
with reunds ef hemp or cotton, loosely spun or twisted, 
which is pressed into a pretty compact form by a ring B,d, 
which is worked down by screws distributed round the 
ring and working into the body of the piston; by which’ 
means the packing is made to fill the diameter of the cy- 
linder pretty closely, and to prevent, while the packing re- 
mains sound, any steam from passing between the piston 
and the cylinder. In the usual method, whenever the pis- 
ton, by continued working, becomes too easy, and so occa- 
sions a waste of steam, it is necessary to take off the top of 
the cylinder, even when fresh hemp or cotton is not wanted, 
merely to get at the screws, which serve to force the upper 
ring nearer to the bottom of the piston, by which means 
the packing is forced outwards against the side of the cy- 
linder. This is beavy laborious work, and is therefore ge- 
nerally shunned by the man that attends the engine, as long 
as the engine can possibly be made to work without taking 
this Souble ; and in consequence of this neglect a great and 
unnecessary waste of steam is pacaaacede. and a waste of 
fuel. in proportion. é 
Mr. 
