ON THE MANUFACTURE OF SULPHURIC ACID. 109 
nates near the ceiling of the other; this latter then commu- 
nicates with the large chamber in the same manner. 
The communication between the large chamber and the 
third, and between the third and fourth chambers, is somewhat, 
different; the pipe connecting the largest chamber with the 
next is smaller in size than the former pipes of communication, 
and commences in a similar manner near the floor; after its 
exit from the large chamber it descends and enters the top of a 
box; from this box a second pipe ascends and enters near the 
ceiling of one of the second size chambers. From this chamber 
a similar pipe passes out, forming a communication with the 
last chamber, the same in every respect as that just described. 
The last chamber has the same kind of pipe and box, but 
instead of being connected with another chamber, it commu- 
nicates with the external air by means of a long terminal pipe. 
The boxes mentioned are intended for the condensation of 
such acid vapours as escape condensation in the preceding 
chambers. Besides these pipes of communication for the con- 
veyance of the acid vapors, there are small tubes by which 
the acid on the floor of the smaller chambers may be conveyed 
to the larger; the second chamber is thus connected with the 
first and this latter with the large chamber, while the last is in 
the same way connected with the fourth and this again with 
the large chamber; all these communications being commanded 
by stop cocks. In the sides of each chamber there are holes 
so arranged near the floor as to allow the inspection of the 
depth of the liquid and the withdrawal of a portion for exami- 
nation. There are also doors in the side, and in the top a hole 
for the examination of the interior of each chamber. In the 
second chamber are placed several earthenware vessels each 
one higher than the next in succession, in such a position that 
when overflowing, the contents of the first may fall into the 
second, of the second into the third, and so on, those of the 
last falling on the floor of the chamber. A glass tube bent in 
the form of a syphon passes through the side of the chamber 
and goes to the bottom of the first vessel; this tube is connected 
at the other end by a stop cock with a glass funnel. This 
