116 GAS LIGHTS. 
Gas Lights. bottom of the retort ; this prevents the immediate ac- 
PLaTE 
CCLXIV. 
Fig. 7. 
Fig. 6. 
tion of the flame upon the retort, which would soon 
destroy it. The retort, notwithstanding this apparent 
power, ultimately receives the whole of the heat with- 
out being liable to oxidation. When the retort is 
charged, and the lid secured, the gas and the other vo- 
latile pre cts rise through the pipes s and v, and enter 
the larg. ¢ c, which is called the condenser ; see 
Fig. 7. _ «portion of the tar, &c. condenses in this ves- 
sel; till it rises to the level of the pipe z, along which 
the gas and tar descend through a succession of pipes, 
passing round the inside of the vessel AB, which is filled 
with cold water. This vessel is square, so that the 
pipes passing along its sides are of equal length. They 
are so inclined to the horizon, as to come to the point v 
when they have passed quite round the vessel. The 
pipe v x now brings it out atthe point zc. This pipe 
continues its direction into the vessel, Fig. 6. which can- 
not be seen in the profile, Fig. 7. The gaseous pro- 
ducts rise up the pipe /, Fig. 7, and then descending, 
terminates in the vessel L; the plan of which is Fig. 
5. The tar and ammoniacal liquor condense in the ves- 
sel, Fig. 6. which is called the tar vessel. It is made 
perfectly air tight, and its contents are drawn off at 
an aperture on a level with the bottom, so that no air 
can escape till the whole of the liquid is discharged. 
We now return to-the gaseous products, which en- 
ter the vessel L; and in order the better to see how 
they are dispossed of, it will first be necessary to de- 
scribe its office. The vessel in Fig. 7. is a reser- 
voir to contain a mixture of lime and water, for the 
purpose of supplying the vessel L. The vessel m is 
of a limited depth, in order just to supply the vessel 
L to a certain height. The transfer from m to L is made 
by means of the pipe p, by drawing out the plugs. As 
soon as the vessel L has received its proper quantity, the 
plug is replaced. The gas enters ato. The lime water, 
which now stands at the level of the top of the vessel 
m, is pressed down to the point d. The same quantity, 
rising along the passage de fg, reaches to the point g. 
The. gas now enters at d, and passes to e, ie re- 
turning, ascends to /; from whence it rises up to g, 
where it enters the pipe ) c, and the larger pipe J, 
which surrounds 4c. _ The pipe / is closed at the top, 
but below the height / it is perforated with a number 
of holes. The vessel AB is filled with water up to the 
lower extremity of the vessel D, When the gas has 
passed out at the top of bc, it displaces the water in J, 
which is on a level with that in AB, till it sinks to 1. 
It now escapes at the holes above mentioned, and bub- 
bles through the water. In this state it is preserved in 
the gazometer, and is fit for burning, The gazometer we 
shall now explain more particularly. It may be first 
proper to return to the lime vessel L. The cavity 
def g is formed by six plates of iron, lead, or wood, of 
the width of the vessel L, arranged in pairs parallel to 
each other, forming cells, which contain a stratum of 
fluid three inches thick, fifteen inches wide, and of a 
length equal to de added to ef added to fg. This ca- 
vity, and the space L, constitute the whole of the capa- 
city of this vessel, which is employed for the liquid, the 
rest being shut out by the partition 3 d, and the plates 
forming the zig-zag cavity. The gazometer, which re- 
ceives the gas after it has been purified by the lime wa- 
ter, consists of an outer vessel AB filled with water. 
It is made of cast pa apy screwed together by flan- 
ges. D isa vessel e of plate iron, the plates being 
united by rivets. This vessel, in an inyerted position, 
falls and rises in the outer vessel as more or less gas is 
contained in it. For this purpose it is suspended by Gas 
chains, which pass over the pullies 1, 2. ‘The ends of 
both these chains are fastened in separate grooves in Prare 
the edge of the pulley M, which is of such a diameter €CLXI 
that the vessel D rises to its full height before the pulley Fig: 7. 
makes one revolution.- In another groove in the edge 
of the pulley M, is fastened the end of a second chain; 
to which the weight W is suspended. This weight is 
nearly equal to the weight of the vessel D, and assists 
it in rising as the gas comes under it. It will be évi- 
dent, that when the whole of the vessel D is immersed 
in the water, it will become as much lighter as is equal 
to its own bulk of water. | The. vessel will therefore re= 
quire a greater counterpoise as it rises higher, and will 
be the heaviest when it is at the top. This is compen- 
sated by forming the groove in the pulley M, which con- 
tains the weight chain so as to make the radii of the 
wheel change reciprocally with the relative weight of 
the vessel D, by which the pressure of this vessel, which 
is always a little heavier than the weight, will -be uni+ 
form in every part of its ascent and descent. Before 
the gas can be admitted, the vessel D is allowed to de- 
scend to the bottom of the vessel AB, which is effected _. 
by opening the stop cock y in the pipe zq¥, which 
opens into the gazometer above the water. ihe com- © 
mon air is expelled, and its place occupied by water. — 
The cock y is now shut, and the gazometer is ready to ~ 
receive the gas. ah A ee 
We have already traced the progress of the gas to 
the lime vessel, where it is purified. It now rises 
through the pipe c, as has been already described. 
When the cock y is opened, the preponderating weight 
of the vessel nf forces the gas along the pipe z q y, 
from which it is conveyed by other branches into situas 
tions where the light is required. The pipes T and 
i are firmly Se Me into the top of the vessel D, and’ 
in their motion up and down constantly envelope the 
tubes bc and gz. They are for no other purpose than 
keeping the vessel ly D in its ascent and descent, 
That part of each projecting above the vessel, forms a 
recess for the reception of the ends of the pipes 6 ¢ and 
2q, in order that the mouths of the latter may be above 
the water, when the roof of the vessel D comes to the 
surface. Without this. contrivance, the whole of the 
common air at the commencement could not be expell« 
ed. It will-be easy to see, that, from improper manage- 
ment, the gas may, under some circumstances, come 
over so rapidly as to raise the vessel D quite to the top, 
and, still accumulating, would bubble out at the lower 
edge of the vessel, Such gas mixing with the common 
air of the room, would be liable to explode by the light 
of a candle ; indeed, several serious accidents have al~ 
ready happened from this cause. There are several 
ways of avoiding the danger attendant on this circum- 
stance, but the most effectual we have yet seen, we 
shall explain by Fig. 8. AB is a section of the outer Fig. 8. 
vessel of the gazometer, D the inner vessel, p a pi 
inserted in the top of the latter open at both ends 
the lower end being above the surface of the water, 
while the vessel D remains a little immersed. The 
part. dc petra. of a larger tube, with a bottom 
~~? in ea 
. 
een a 
which is orated to receive the pipe p, to which it 
is soldered, so as to form a recess capable of holding 
water, and hence has been called a water-lute. When 
another pipe, such asf, has been placed in the recess 
filled with water, a meres fluid passing up p, would 
be induced to pass ugh f, if not resisted by a force 
less than the column of water at the recess bc. It will 
now be evident, that if the tube f be fixed in the roof 
3 
