ISO History of Mechanical Inventions and useful Processes. 
is driven entirely round. A pinion upon the axle of q , works 
m the wheel which carries the index round a dial-plate, and 
thus registers the quantity of gas which has passed uniformly 
through the aperture c. 
Should the pressure of the gas, however, not be uniform, the 
flap of the vessel b will be raised or depressed accordingly, as in- 
dicated by the dotted line When this happens, the connecting 
rods A, i. A;, will raise or depress the lever o, so as to make it 
move through a greater or less arch, and consequently drive for- 
ward a greater or less number of the teeth of the wheel q. Upon 
the arm 7r, is a stop which, when the flap of b descends and 
contracts the passage of the gas, will, by the connecting arms, 
h, i, A’, be raised so high as to prevent the lever from being act- 
ed upon by the excentric wheel during a part of its revolution ; 
consequently, the arch described by the lever o, will be smaller, 
and the progress of q and s diminished : but when the flap of 
the vessel 6, is raised, and enlarges the passage for the gas, then 
the stop t will be brought sufficiently low to enable the lever o 
to be acted upon by the periphery of the excentric wheel during 
the whole revolution; in consequence of which, the arch described 
by the lever o, will be greater, and the progress of the wheels q 
and s increased. A nut v , having a right and left screw, is 
employed to adjust the length of the rod k. 
For the purpose of stopping the clock movement, when the 
supply of gas is stopped, a paul lever u rises with the rod k, 
for the purpose of locking the excentric wheel. In order to stop 
the passage of gas when the clock movement requires winding 
up, a pinion upon the axis of the fusee v r orks in the dotted 
toothed arch w w. 
The operation of winding up carries the rack back ; but, as 
the movement goes down, the rack advances, by which a tooth 
.r, upon its axle, presses upon the short end of the lever ?/, which 
it raises, and causes to lift the rod k, at the same time, mak- 
ing the rod A, press down the flap of A, in order to bring the 
aperture c in contact with the plate /,' and thus obstruct com- 
pletely the passage of the gas *. 
* See the London Journal of Arts, No, viii. p. 81. 
