129 
Mr Malanfs Improved Patent Gas Meter. 
ed. Care should be taken that the dye be not too much con- 
centrated : When this happens, the colour is far less bright and 
delicate, and approaches nearer to orange. It is hardly necessa- 
ry to add, that the dye should be boiled, and kept in a brass, or 
some other vessel, into the composition of which iron does not 
enter.” 
9. Description of the improved Patent Gas Meter , by Mr John 
Malam. 
The object of this ingenious instrument is to exhibit upon 
a dial-plate, the quantity of gas which passes through a tube 
in its progress to the burners. It is represented in Plate I. Pig. 15. 
where a is the pipe through which the gas passes that is to be 
measured ; h an air tight vessel, like bellows, with the upper flap 
rising or falling upon a joint or hinge, and constructed of leather 
or cloth, protected against the chemical action of the gas. 
Prom this vessel the gas escapes through the aperture c, into 
the outer case d d, and thence through the exit-pipe c, to the 
burners. The aperture c, is partially closed by the flat plate f 
suspended or swinging upon the rod g , and accommodating it- 
self to the descent of the flap. 
When equal quantities of gas pass along, in the direction 
«, f b , c, d, <?, in equal spaces of time, which is generally the 
case, the quantity of gas will be indicated by the clock move- 
ment shewn in the upper part of the figure, provided the clock 
always stops with the supply of gas, and goes again when the 
supply recommences ; for effecting which, there is a particular 
contrivance, which shall be afterwards described. The clock 
movement in the cylindrical box /, supported and fixed upon legs 
m to, gives motion to an axle carrying a small exccntric wheel, 
or crank n , in order to raise the lever o, which has its fulcrum 
on the axle of the wheel q , and rests upon the pheriphery of the 
excentric wheel. The lever being thus raised, a small spring 
catch p, attached to it, takes into the teeth of the wheel g, and 
when the lever again descends, the catch drives the wheel round 
a short way. Another spring r 9 holds the wheel as the lever 
again rises ; and, in this manner, by many revolutions of the ex- 
centric wheel n 9 raising and lowering the lever o, the wheel q 
VOL. V. NO, 9. JULY 1821. I 
