410 Messrs. Galloway and O'Farrell on some 
cleaned when required. It has the usual fittings, such as the 
water-gauge, the pressure-gauge, and the safety-valve. By 
the arrangement shown in the Plate, distilled water can be 
obtained from it j and a steam-pipe (not shown in the Plate) 
could also be connected with it for the purpose of supplying 
steam to an open air-bath, this bath not being connected, as 
those shown in the Plate are, with the air-pump. 
The engine, B, is of the donkey-pump type, with one in- 
verted cylinder whose rod acts directly on the air-pump C. 
D is the ordinary vessel for the exhaust steam to escape into 
after having performed work in the engine ; it is from there 
conveyed, if required, directly, or after it has been superheated, 
or a mixture of the two (normal and superheated steam), into 
the steam-jackets of the vessels E and F. If it is not required 
to heat these vessels, it is carried away through the pipe a on 
opening the stopcock b into the escape-pipe or chimney c. 
G represents a filtering-apparatus in position ; and H a 
retort and receiver for carrying on distillations under dimi- 
nished pressure. 
The downward pipes marked d from the vessels E and F, 
and the longer pipe e, in which they terminate, form together 
the suction-pipe in connexion with the different pieces of appa- 
ratus and with the air-pump ; it terminates, as shown in the 
Plate, in the air-tight box I, in which terminates also the pipe/ 
from the air-pump. This box is provided with an overflow- 
pipe for carrying off the excess of water which accumulates 
from the aqueous vapour conveyed from the vessels E, F, G, 
and H by the suction-pipe. A vacuum-gauge g maybe attached 
to the box I; it would of course indicate the vacuum through- 
out the entire system ; but if it was considered desirable to 
ascertain more accurately the vacuum in any one or all of the 
different pieces of apparatus, a separate mercurial gauge would 
be required in connexion with the particular apparatus, as 
will be presently noticed. 
Little further description is required as regards the appa- 
ratus G and H ; we have not considered it necessary to illus- 
trate a condenser in connexion with the retort and receiver. 
The filtering-apparatus shown is one for large non-quantitative 
operations: if the filtrate is required, it will be seen from the 
drawing that portions of it can be drawn off from time to 
time by means of the tap for evaporation or for other pur- 
poses, whilst the filtration or washing is taking place, without 
interfering with the vacuum. It need scarcely be observed 
that quantitative filtrations can be as conveniently carried on ; 
and that many filtrations and distillations are capable, by this 
svstem, of being carried on at the same time. 
