320 
cause the valve in the piston remains shut by 
its own weight. The air, therefore, is driven 
through tiie valve L, into the rising-pipe, 
and escapes. In the mean time, the air 
which occupied the small space between the 
piston and tiie valve T, expands into the 
upper part of the working-barrel ; and its 
elasticity is so much diminished thereby, 
that the atmosphere presses the water of the 
cistern into the suction-pipe, where it rises 
until an equilibrium is again produced. The 
next stroke of the piston downwards, allows 
the air which had come from the suction-pipe 
into the barrel during the ascent of the 
piston, to get through its valve. Upon draw- 
ing up the piston, the air is also drawn off 
through the rising-pipe. Repeating this pro- 
cess, brings the water at last into the working- 
barrel, and it is then driven along the rising- 
pipe by the piston. 
This is one of the best forms of a pump. 
The rarefaction may be very perfect, because 
the piston can be brought so near to the bot- 
tom of the working-barrel: and for forcing 
water in opposition to great pressures, it ap- 
pears preferable to the common forcing- 
pump ; because in that, the piston-rod is 
compressed and exposed to bending, which 
greatly hurts the pump, by wearing the piston 
and barrel on one side. This soon renders 
it less tight, and much water squirts out by 
•the sides of the piston. But in this pump the 
piston-rod is always drawn, or pulled, which 
Keeps it straight, and rods exert a much 
greater force in opposition to a pull than to 
compression. The collar of leather round 
the piston-rod, is found by experience to be 
very impervious to water ; and though it 
needs but little repair, yet the whole is very 
accessible ; and in t^liis respect much prefer- 
able to the common pump, in deep mines, 
where every fault of the piston obliges us 
to draw up some hundred feet of piston- 
rods. By this addition too, any common 
pump, for the service of a house, may be 
converted into an engine for extinguishing 
lire, or may be made to convey the water 
to every part of the house ; and this without 
hurting or obstructing its common uses. All 
that is necessary", is to have a large cock on 
the upper part of the working-barrel, oppo- 
site to the lateral pipe in this ligure. 'This 
cock serves for a spout, when the pump is 
used for common purposes; and the merely 
shutting this cock, converts the whole into 
an engine for extinguishing fire, or for sup- 
plying distant places with water. It is 
scarcely necessary to add, that, for these 
services, it will be requisite to connect an 
air-vessel with some convenient part of the 
rising-pipe, in order that the current of 
water may be continual. 
It is of considerable importance, that as 
-equable a motion as possible is produced in the 
.maiit-pipe, which diminishes those strains 
which it is otherwise liable to. The appli- 
cation of an air-vessel at the beginning of the 
pipe, answers this purpose. In great works, 
it is usualfo effect this by the alternate action 
of two pumps. It will be rendered still more 
uniform, if four pumps are employed, suc- 
ceeding each other at the interval of one 
quarter of the Aime of a complete stroke. *< 
But ingenious men have attempted the 
same thing with a single pump ; and many 
different constructions for this purpose have 
been proposed and executed* lug. 5, re- 
PUMP. 
presents one of the best. It consists of a 
working-barrel, ab, closed at both ends ; the 
piston c is solid, and the piston-rod passes 
through a collar of leathers at the top of the 
barrel. This barrel communicates laterally 
with two pipes, n and k, the communications 
being as near to the top and bottom of the 
barrel as possible. At each of the communi- 
cations are two valves, opening upwards. 
The two pipes unite in a larger rising-pipe at 
b, which bends a little back, to give room 
for the piston-rod. Suppose the piston down 
close to the entry of the lateral pipe h ; when 
it is drawn up, it compresses the air above 
it, and drives it through the valve in the pipe 
A, whence it escapes through tire rising-pipe; 
at the same time it rarefies the air below it. 
Therefore the weight of the atmosphere shuts 
the valve in, and causes the water in the cis- 
tern to rise through the valve n, and till the 
lower part of the pump. When the piston is 
pushed down again, this water is first driven 
through the valve in, because n immediately 
shuts ; and then most of the air which was 
in this part of the pump at the beginning, goes 
up through it, some of the water coming back 
in its stead. In the meantime, the air which 
remained in the upper part of the pump after 
the ascent of the piston, is rarefied by its 
descent; because the valve o shuts as soon 
as the piston begins to descend, the valve p 
opens, the air in the suction-pipe It expands 
into the barrel, and the water rises into the 
pipes by the pressure of the atmosphere. 
Tiie next rise of the piston must bring more 
water into the lower part of the barrel, and 
must drive a little more air through the valve 
o, namely, part of that which had come out 
of the suction-pipe li ; and the next descent 
of the piston must drive more water into the 
rising-pipe k, and along with it, most, if not 
all, of the air which remained below the 
piston, and must rarefy still more the air 
remaining above the piston ; and more water 
will come in through the pipe h, and get into 
(he barrel. It is evident, that a few repe- 
titions will at last fiii the barrel on both sides 
of the piston with water. When this is ac- 
complished, there is no difficulty in perceiving 
how, at every rise of the piston, the water of 
the cistern will come in by the valve n, and 
the water in the upper part of the barrel will 
be driven through the valve o; and in every 
descent of the piston, the water of the 
cistern will come into the barrel by the valve 
p, and the water below the piston will Be 
driven through the valve in ; and thus there 
will be a continual influx into the barrel through 
the valves n and p, and a continual discharge 
along the rising-pipe l through the valves 
m and o. 
This machine is certainly equivalent to 
two forcing-pumps, although it has but one 
barrel and one piston ; but it has no sort of 
superiority. It is not even more economical, 
in most cases ; because, probably, the ex- 
pence of the additional workmanship will 
equal that of the barrel and piston, which is 
saved. There is, indeed, a saving in the rest 
of the machinery, because one lever pro- 
duces both motions. It therefore cannot be 
called inferior to two pumps ; and there is 
undoubtedly some ingenuity in the contri- 
vance. 
Fig. 6, is another puiffp for furnishing a 
continued stream, invented by Mr. Noble. 
AB, the working-barrel, contains two pistons, 
i C and B, which are moved up and down al- 
| ternately by the rods fixed to the lower F, 
I The rod of the piston B, is carried through 
the piston or bucket C. This pump is very 
simple in its principle, and may be executed 
at little expence. 
The pump invented by M. De la Hire, 
raises water equally quick by the descent as 
by the ascent of the piston in the pump- 
barrel. 
AA (fig. 7), is a well, in which the lower 
ends of the pipes B and C are placed. D is 
the pump-barrel, into the lowermost end of 
which the top of the open pipe B is soldered, 
and in the uppermost end the hollow pipe S 
is soldered, which opens into the barrel ; and 
the top of the pipe C is soldered into that 
piece. Each of these pipes has a valve on 
its top, and so have the crooked pipes E and 
F, whose lower ends are open into the pump- 
barrrel, and their upper ends into the box 
G. L is the piston-rod, which moves up 
and down through a collar of leather in the 
neck M ; K is a solid plunger, fastened to 
the rod or spear L ; the plunger never goes 
higher than K, nor lower than D ; so that 
from K to D is the length of the stroke. 
As the plunger rises from D to K, the at- 
mosphere (pressing on the surface of the 
water A A in the well) forces the water up the 
pipe B, through the valve b, and fills the 
pump-barrel with water up to the plunger ; 
and during this time, the valves e and S lie 
close and air-tight on the tops of the pipe# 
E and C. 
When the plunger is up to its greatest 
height, at K, it stops there for an instant, and 
in that instant the valve b falls, and stops the 
pipe B at top. Then, as the plunger goes 
down, it cannot force the water between K 
and D back through the close valve b ; but 
forces all that water up the crooked pipe E, 
through the valve e, which then opens up- 
ward by the force of the water ; and this 
water, after having filled the box G, rises into 
the pipe N, and runs off by the spout at O. 
During the descent of the plunger K, the 
valve/ falls down, and covers the top of the 
crooked pipe F ; and the pressure of the at- 
mosphere on the well AA forces the water 
up the pipe C, through the valve S, which 
then opens upward by the force of the as- 
cending water; and this water runs from S 
into the pump-barrel, and fills all the space iit 
it above the plunger. 
When the plunger is down to its lowest 
descent at D, and stops there for an instant, 
in that instant the valve S falls down, and 
shuts the top of the pipe C ; and then, as the 
plunger is raised, it cannot force the water 
above it back through the valve S, but drives 
all that water up to the crooked pipe F, 
through the valve/, which opens upward by 
the force of the ascending water; w'hich 
water, after filling the box G, is forced up 
from thence into the pipe N, and runs off by 
the spout at O. 
And thus, as the plunger descends, it forces 
the water below it up the pipe E; and as it 
ascends, it forces the water above it up the 
pipe F: the pressure of the atmosphere filling 
the pump-barrel below the plunger, through 
the pipe B, while the plunger ascends ; and 
filling the barrel with water above the plun- 
ger, through the pipe C, as the plunger goes 
down . 
Thus there is as much water forced up the 
