MAGAZINE OF SCIENCE AND ART. 
215 
cylinder was surrounded with a wooden casing, 
leaving an intermediate space of seven inches. 
This space was filled with saw-dust. The top of 
the cylinder had also a false cover in order to 
prevent any radiation of heat, and the engine- 
house is thus always kept cool. 
The balance-beam of the engine was 37 feet 
8 inches in extreme length, and weighed 22 tons. 
Tt was foxined of two cast-iron plates, 5 feet 6 
inches in depth at the centre, and connected to¬ 
gether by the main gudgeon, the pump gudgeons, 
and by screw-bolts. The length of the two 
arms, measured irom the centre, differs by two 
feet, the longer arm. being at the cylinder end. 
The object of thus placing the fulcrum of the 
balance-beam out of the centre is to reduce the 
velocity of the column of water in the pumps, 
and thus diminish the concussion or blow upon 
the pump valves. 
The engine worked two pumps of the respec¬ 
tive diameters of 34 inches and of 20 inches, the 
34 inch pump having a length of stroke of 10 
feet, and the 20 inch pump a length of stroke of 
7 feet 4 inches. 
Either of these pumps could be disconnected 
and worked separately, and the operation of de¬ 
taching one or the other was effected in a very 
short space of time. The pump3 are of the kind 
called “plunger” pumps, being formed of a hol¬ 
low cylinder of iron, the length of which is a 
iitti greater than the length of stroke. .These 
cylinders are turned accurately on the outside, 
and brought to the exact diameter required; the 
hollow part of the cylinder is filled with a cast- 
iron filling piece which adds to their weight. 
The pump-valves were of a novel and inge¬ 
nious construction, being the invention of a 
Cornish engineer, Mr. K. Hosking. Being little 
known out of Cornwall, and their application at 
the Vanxhall Water Works being their first in¬ 
troduction in a water works' engine, a short de¬ 
scription of them may prove not uninteresting, 
The valve is an annular one, and consists of 
three concentric rings arranged pyramidally, 
and resting one upon the other, thereby afford¬ 
ing a free passage for the water around the cir¬ 
cumference. Tho upper ring is attached to a 
stalk, and the two lower ones have internal 
wings, which serve as guides when the rings are 
in motion. 
The chief advantages offered by these valves 
consist in an increase of water way, and in a 
reduction of concussion, for as the blow caused 
by the shutting of pump-valves is in proportion 
to the surface in contact and to the square of the 
height or distance passed through while in the 
act of shutting, the greater the number of parts 
of whicli the valve is composed, the greater will 
he the freedom of water way, and consequently 
the burthen on the engine and the concnssion 
will be proportionally diminished. 
These valves succeeded perfectly at Yauxhall, 
and they have since been introduced into other 
pumping-engines, being superior to any other 
kind of valve whether for mining or for water 
works’ purposes. 
The well in which the pumps were placed is 
32 feet in depth, and as the tide from the river 
flowed into this well, the whole height to which 
the water was required to be raised by the large 
pump did not exceed 20 feet; the water from 
this pump being delivered into a, large tunnel- 
pipe of 42 inches diameter, through which it 
flowed into two large reservoirs. The smaller 
pump was intended to supply a part of the dis¬ 
trict through a 20 inch main pipe. 
The plunger pump is generally to he preferred 
to the common piston pump, because the pump- 
barrel of a plunger pump docs not require to be 
bored, as is the ease where a piston is used : and 
another advantage is, that the packing of the 
stuffing-box round the plunger is much more 
easily kept in order than the packing of a 
piston. In the former ease any defect in the 
packing can he seen and remedied at once; 
whereas the latter being out of sight is often al¬ 
lowed to become leaky and defective before the 
fault is discovered. 
The feed-pump for supplying the boiler with 
water is also a plunger-pump, having a diameter 
of <U inches, with a length of stroke of 2 feet 
9 inches. It delivers about 2f gallons at each 
stroke, being rather more thsn’sufficient for the 
supply of the boilers. 
The boilers of which there were four to this 
engine are 33 feet in length by 5 feet 4 inches in 
diameter. The ends of the boilers are flat, and 
are formed of plates Of half an inch rolled iron, 
rivetted to the top and side plates by means of 
J internal angle-irons. Thu angie-iron is bent 
round the boiler, and forms an exceedingly 
strong and efficient mode of connection. 
Each boiler had a cylindrical flue or fire- 
tube 3 feet 3 inches in diameter, extending 
throughout the whole length of the boiler, and 
placed within seven inches of the bottom. The 
furnace is contained within this tube; it is fixed 
at the height of 1 foot 7 inches above the bot¬ 
tom, and exposes a superficial area of 12 square 
feet. 
In the setting of the boilers, each boiler rests 
upon three cast-iron “horses,” which are placed 
in the bottom flue, and oiler little or no resis¬ 
tance to the passage of the heated air beneath 
the boiler. This flue is 1 foot 8 inches in height 
by 2 feet 11 inches in width, the side flues are 
10 inches in width and 3 feet 9 inches in height. 
The flame and heated air pass in the first place 
through the fire-tube to the furthest end, where 
dividing they return along both side flues to the 
front of the boiler, and then descending the two 
currents unite and pass under the boiler to the 
end, where they enter the flue which leads to the 
chimney shaft. 
The steam-tube is a cylinder 30 feet in length 
hy 2 feet 0 iuches diameter, and is formed of 
plates of the same thickness as those of which 
the boilers are composed (7-10) of inches. It is 
placed in the transverse direction of the four 
boilers, and is united to each of them by means 
of a short connecting pipe. 
The use of this tube (and it is an important 
one) is to form a chamber or Teceptacle for the 
steam previous to its passing into the cylinder. 
Where, as is usually the ease with the Cornish 
boiler, very little steam room is afforded, this 
tube is indispensable in forming a receptacle for 
the steam. 
The pressure of the steam in tho boilers is re¬ 
gulated by the moveable weights attached to the 
levers of the safety valves, one of which ig fixed 
over each boiler. The valve itself is of the ordi¬ 
nary form of mitre valve, and is four inches in 
diameter. It, as well as the valve seat, is of 
