42 Improved Eudiometrical Apparatus, by Dr. Hare- 
_ [ti is well known, to those who are familiar with pneamat~ 
air pump, and a barometer gage, the extent of the exhaus- 
tion will * indicated by the height of the mercury im the 
gage tube; so that if there be a ‘scale of equal parts asso- 
ciated with “ tube, the quantity of air taken from the re- 
ceiver at any stage o of the exhaustion, will be to the quantity 
held by it — me as the number opposite the mereurial 
column, when observation is made, to that to which it 
would rise, if da receiver were thoroughly exhausted. 
ence having exhausted the vessel, thoroughly, if the 
mercury stand at 450 degrees, by the gage, on allowing any 
gaseous fluid to enter Res it sinks to 150°, the quantity in 
the receiver will be 300 parts; and if of this, by explosion, 
or any other means, any number of parts be condensed, the 
mercury in the gage must rise that number of degrees.* 
In order to have a receiver strong enough to resist explo- 
sion, and at the same time sufficiently capacious to hold quan- 
tities of gas many times larger than have heretofore been ex- 
ploded at once, I have provided a stout tube, six feet in length, 
tapering from two inches to one inch in diameter internally ; 
open at the larger, and closed ut the smaller end. 
This tube is cemented, at the larger end, into a brass fer- 
lug screws, through which are inserted stout wires, one of 
them insulated, for producing galvanic ignition in an are of 
platina wire, as already described im the case of my other 
’ eudiometers.t 
* That portion of the bore of the tube which is not occupied by mercury, 
adds to the capacity which influences the gage, and the € por rtion of the gage 
which is emptied of mercury, varies in extent; butasthe air, which remains 
_be remedied by te, or + eine the dish, by an appropriate screw, or em- 
een dish of a Len gras so large, and. aga ge tube with a bore so small, 
ato nae 1 Eshe f the rise, or subsidence of the mercury i ’ 
3 greatest oo which I encountered, was in the ee 
best of stprestoy i in common form. This I obviated by two con- 
thine of% own; one i iv wenited about tixteen es pene s ago, the other in the 
of | Of the: I shall publish a description, cin engravings. 
convwiniently. 
* 
