Dr. Hare's knproved Eadiometers. 75 
(fig. 1.), excepting that instead of carrying the Kudiometer to 
the calorimotor, the circuit is established by lead ods seve- 
rally attached to the galvanic poles, by gallows and screws. 
(see gg fig. 2.) One of the lead rods ierminates in a piece 
of iron, immersed in the mercury, the other is fastened to the 
insuiated 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 anticipated.. A communication with the 
gauge must then be opened gradually. If the water is dis- 
turbed from its level, the equilibrium 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 oxygen 
gas in the included air. Or, the residual air being expelled 
by the rod, and the quantity thus ascertained deducted 
from the amount included before tie explosion, the differ- 
ence will be the quantity condensed. — 
"It may be proper to mention, that as other metals are al- 
most universally acted upon by mercury, the cocks, sockets, 
screws, and sliding-rods of the mercurial Eudiometers, are 
made of cast steel. The tubes containing the rods, are of 
iron. 
Since the drawings (figs. 1 and 4) were made, verniers 
have been attached to the screws, through which the sliding=- 
rods pass; so that the measurements are made to one-tenth 
of a degree. 
Ihave alluded to the water gauge without explaining’ its 
construction. It consists of three tubes. A small tube of 
varnished.copper, (which is fastened into the only perforation 
which communicates with the cock, and of course with the 
glass recipient,). passes up in the axis of a glass tube ¢T. fig. 
4.) open at top, 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 
iube in its axis. This intermediate: glass tube is open 
at its lower termination, but at the upper one is cloge-q: oy 
pened at pleasure by ascrew. The interstices betweet the 
