38 Improved Eudiometrical Apparatus, by Dr. Hare. 
SIMPLE VALVE VOLUMETER. 
Besides the lower orifice, O, by which 
© J it is filled with gas, the volumeter, which 
this figure represents, has an orifice at 
its apex, A, closed by a valve attached 
toa lever. This lever is subjected to a 
spring, so as to receive the pressure re- 
quisite to keep the upper orifice shut, 
when no effort is made to open it 
When this volumeter is plunged be- 
low the surface ofthe water of a pneu- 
matic cjstern, the air being allowed to 
escape, and the valve then to shut itself 
under the water, on lifting the vessel, it 
comes up full of the liquid, and will re- 
main so, if the lower orifice be ever so 
3 low the surface of the water in 
a the cistern. Thus situated, it may 
filled with hydrogen, proceeding, by a 
Oo fe sacl) tube, from a self-regulating reservoir. 
acd: If the apex, A, be then placed under 
any vessel, inverted duly in the usual way, the gas will pass 
4nto it, as soon as the valve is lifted. 
Volumes of atmospheric air are taken, by the same instru- 
ment, simply by lowering it into the liquid of the cistern, 
placing the apex under the vessel into which it is to be trans- 
ferred, and lifting the valve ; or preferably by filling it with 
water, and emptying it in some place, out of doors, where 
the atmosphere may be supposed sufficiently pure, and after- 
wards transferring the air, thus obtained, as above described, 
¥ opening the valve while the apex is within the vessel in 
which the mixture is to be made. In this case, while carry- 
ing the volumeter forth and back, the orifice must be closed. 
This object is best effected by a piece of sheet metal, or pane 
of glass. 
It is necessary that the water, the atmosphere, and the 
— should be at the same temperature during this pro- 
