Dr. Hares Improved Eudiometers. te 
(fig. 1 ): excepting _ deve of re the Eudiometer to 
the calorimotor, the circuit is established by lead -ods seve- 
rally sina to the patie poles, by gallows and screws. 
(see gg fig. 2.) One of the lead ae terminates in a piece 
of iron, immersed in the mercury, the other is fastened to the 
‘inesiagd wire of the Eudiometer. Under these circum- 
stances, one of the calorimotors is surrounded with the acid 
contained in the jug, and an explosion almost invariably suc- 
ceeds. Before effecting the explosion, the number of the 
degrees of the sliding-rod, which are out of its tube should be 
noted; and it must afterwards be forced into the tube, in order 
to compensate the consequent condensation of the gases, as 
nearly as it can be ceaced e Pas <a with the 
gauge must then be o ly. If the water is dis- 
turbed from its " Svilibriom must be restored 
by duly moving the rod. Then deducting the degrees of the 
sliding-rod, remaining out of the tube, from those which it 
indicated before the explosion, the remainder is the deficit 
caused by it; one-third of which is the quantity of —, en 
gas in the included air. Or, the residual air being ex 
by the rod, and the quantity thus ascertained deducted 
from the amount included before te explosion, the differ- 
ence will be the quantity condensed. 
may be proper to mention, that as other metals are al- 
most universally acted upon by mercury, the cocks, sockets, 
screws, and slidiag-rods of the mercurial Eudiometers, are 
made of cast steel. The tubes containing the rods, are of 
iron. 
Since the a (figs. 1 and 4) were made, verniers 
have been attached to the screws, through which the sliding- 
rods 3 so that the measurements are made to one-tenth 
of a degree. 
I have alluded to the water gauge without explaining its 
construction. It consists cr three tubes. A small tube of 
varnished copper, (which is fastened into the only perforation 
which communicates with the cock, _ of asain "T “9 
lass recipient,) passes up in the axis of a glass tu 
5) open am , cemented into a socket, (S, fig. 4.) which 
screws on to the cock. A smaller glass tube is placed in the 
interstice between the external glass tube and the copper 
tube in its axis. This intermediate glass tube is open 
at its lower termination, but at the upper one is closed or 
opened at pleasure by ascrew. The interstices between the 
