40 Improved Eudiometrical Apparatus, by Dr. Hare. 
The construction of this instrument differs from that of my 
sliding rod eudiometers, in having a valve which is opened 
and shut by a spring and lever, acting upon a rod passing 
bee = a collar of leathers. By means of this valve, any 
gas, drawn into the receiver, is included so as to be free from 
the possibility of loss, during its transfer from one vessel to 
ther. This instrument is much larger than the eudiome- 
nas: for Selec, — intended to make mixtures of gas, 
n those cases where one is to be to the other, in a proportion 
which annot be conveniently obtained by taking more or 
less volumes of the one, than the other, by means of the vo- 
lumeters ; as, for instance, suppose it were an object to ana- 
lyze the air, according to Dr. Thomson’s plan of taking 42 
per cent. of hydrogen. ‘The only way of mixing the gases 
the volumeter 21 times of hydrogen, and 50 times of atmos- 
pheric air. By the large sliding rod instrument, this object 
is effected at once by taking 42 measures of the one, and 
100 measures of the other. 
BAROMETER GAGE EUDIOMETER. 
The following is an epcraving of the barometer gage eudi- 
ometer for explosions. R, is a glass receiver. Within the 
receiver, near W, is an arc of platina, by the feaicios of 
which the gas is inflamed. C, is a cock with three orifices, 
either of which may be made to communicate with the re- 
ceiver, according to the position of the lever, L. More than 
of the orifices cannot be open at once, but all may at the 
same time be closed. The barometer gage, G G, is seen be- 
side the receiver, with which it communicates through the 
pipe P, and the valve cock V, by means of which the com- 
munication, between the gage and the receiver, may be sus- 
pended at pleasure. The pipe A, conveys to the receiver, 
the gaseous mixture from the bell glass B. By one of the 
pipes D, a communication with “ty air pump may be ord 
lished. The other pipe is used when different kinds of gas 
are to be successively introduced; or when or of te. 
sidual gas is to be drawn out for examination. T T, are 
rods for conveying the ignition to the platina wire. m, is a 
wooden dish, holding mercury for the gage tube.. 
