EXPLANATION OF THE PLATES. 
381 
M, Is the air pump, through which the bucket M' discharges the water resulting 
from the condensation of the steam from the cylinder, in its passage through the 
pipes 15 15, together with the air and uncondensed vapour, into the hot well Z, through 
its valve 17, whence it is carried forward by the feed pipes into the boiler A. 
Still, in order to meet unavoidable losses of water from the boilers by the waste of 
steam, &c., a distilling vessel A', of cylindrical figure, is introduced within the boiler, 
which uniformly maintains the requisite height of water therein, in the following 
manner: 
A pipe 18, connecting the upper surface of the still A' with the upper or steam 
chamber 13, of the condenser, is furnished with a stop cock 19, which when open per 
mits the vapour generated in the still to pass over into the condenser, whence it is 
returned by the feed pipes, in addition to the water resulting from the steam of ex 
haustion, into the boilers, and is regulated in quantity by the amount of opening of the 
stop cock 19. 
The connection with the condenser produces a nearly corresponding vacuum in 
the still, whence evaporation takes place at a lower temperature and much more ra 
pidly than if exposed to the atmosphere at the ordinary boiling point of 212°. 
As the evaporation proceeds, and the water in the still becomes lower than the 
level marked in the drawing, the copper float 20, descends, carrying with it the rod 
21, of the index 22, and causing the valve 23 to be lifted at the same time. The 
valve 23, being connected with the supply pipe 24, which is joined at the other ex 
tremity with the waste pipe S of the condenser, affords abundance of sea water to 
pass into the still, until again closed by the float 20; the index 22 exhibiting the 
operation. 
By the frequent repetition of this process, it will be seen that the water in the 
distilling vessel A', will become saturated with salt, and in that respect the still will 
be assimilated, with the exception of risk from burning in case of neglect, to ordinary 
boilers working with sea water; it is also kept clean by the same rule, thus: 
The pipes, 18 and 24, being first shut off from the still by their respective stop 
cocks, a communication is opened by the cock 25, with a pipe 26, which descends 
nearly to the bottom of the still, its other end passing through the ship’s side. At 
the same time, another pipe, (not seen,) also furnished with a stop cock, allows the 
steam from the boiler to pass into the upper part of the still, whence by its pressure 
the brine and other impurities are completely driven out into the sea. 
These latter pipes being shut off and the former ones opened, the process of distilla 
tion goes on as usual. 
The piston B', acting on the cross head D, gives motion to the side rods E, which 
are connected at the lower ends with the beams or main levers C, and these vibrat-