MECHANIC St. 
758 
end of the great hole; and it unferews at the extreme 
end, to fit on jets of different bores, in the lame manner 
as all other fire-engines. In working, the preffure of the 
water condenles the air contained in the receiver into a 
fmall fpace; and its re-action to refume its former bulk 
equalizes the efflux of water from the nozzle of the pump. 
In fome experiments upon this pump, it performed as 
well as could be defired, a fingle pump forming a very 
effective engine; but, when the three were combined, it 
was fuperior in force to any ever feen, and would throw 
a ftream, of an inch in diameter, over the main-top-mall 
head of a 74-gun (hip. If the (hip proves leaky, and the 
Itufling-box is thought to be an obftrurtion to the work¬ 
ing of the pump, the air-velfel may be taken out, in 
which ftate it arts as a common hand-pump ; but the air- 
vefl'el can be reftored to its place, and be ready for work, 
in two minutes. To prevent any of the work being 
neglerted through careleifnefs, the inventor propofes that 
one of the pumps (hall be always ufed to walli the fitip 
by the h'ofe and jet in the morning, which it would do 
much more effertively than by the prefent mode of raifing 
the water into buckets; and the force with which the jet 
of water is thrown would very completely walh into every 
recefs of the gun-carriages, and other places, where a 
brufh cannot reach ; while, by this conftant exercife, the 
pumps would always be ready at a moment’s notice on 
an alarm of fire. 
Mr. Robert Clarke, of Sunderland, has propofed an im¬ 
provement in the mode of applying men’s force to pump¬ 
ing, which is worthy the confideration of feamen. It is 
to change the pofture cf Handing to fitting, and making 
the artion the fame as that of rowing, which, befides that 
it is by philofophers confidered as the moll efficacious ap¬ 
plication of a mail’s force, is to feamen moft particularly 
fo from their habitual prartice of it. He objerts to the 
ordinary artion of pumping with a brake, as the poffure 
is Weak, and requires much force to prelerve it. It op- 
preffes the man by over-ffretching bis loins on one fide,, 
and incommodes refpirAtion, by the flexure of the body 
en the other fide. Too much motion of the fhoulder- 
joint is required, as the mufcles which art on the arm- 
bone at this joint are difproportionate to the effort they 
muff make, when the arm vibrates on the fhoulder-joint 
as a centre, for the force to be communicated by the hand. 
Befides this, the arms theriifelves are at'one inftant en¬ 
feebled, by being thrown above the head, and requiring a 
pull, and the next inftant require a pufhing effort; which 
changes of dirertion in the exeftiort and fultaining force, 
are too continual and rapid for long continuance; in hand¬ 
ing, the body is a continued dead weight upon the legs. 
The artion of rowing is powerful to a furprifing degree, 
and fo well adapted to a man’s eafe, that he can continue 
it a greater length of time without fatigue than any other 
mode of exertion ; for, though the motion is large, it is 
made tip of eafy motions in f'everal joints; the velocity 
and refiffance of which fuit the mufcles employed. Very 
little fultaining force is required, fortlre body is fupported, 
and returns unloaded to its charge: the breathing is free. 
The manner of carrying this into eff'eft is very fimple, the 
lever or brake being bent at right angles at a centre-pin, 
fo that it hangs liraight down when it is at reft, inftead 
of being horizontal; then to the lower extremity a rod is 
jointed, which is carried rather, in an inclined dirertion 
upwards to the feaman, who is feated before the pump 
with a reft for his feet. The rod has a crols handle, to 
hold by both hands, and in fome cafes it may be made 
long enough for two men to fit fide by fide upon the 
fame feat; and, by drawing and pufhing it in the fame 
manner as rowing, the perpendicular lever is caufed to 
vibrate, and the horizontal arm, or bended part, which 
fufpends the pump-fpear, partakes of the motion fufli- 
ciently for pumping. 
The Zurich Machine. —This machine is a kind of pump, 
invented and ererted by H. Andreas Wirtz, an ingenious 
tin-plate worker in Zurich ; and operates on a principle 
different from all other hydraulic engines. The follow¬ 
ing defeription of it, written by Dr. Robifon, is extrarted 
from the Encyclopredia Britannica. 
Fig. 88. Plate XXVI. is a (ketch of the fertion of the 
machine, as it was firlt ererted by Wirtz at a dye-hoafe in 
Limmat, in the fuburbs or vicinity of Zurich. It confifts. 
of a hollow cylinder, like a very large grindffone, turning 
on a horizontal axis, and partly plunged in a ciftern of wa¬ 
ter. The axis is hollow at one end, and communicates- 
with a perpendicular pipe OBZ, part of which is hid by 
the cylinder. This cylinder, or drum, is formed into a 
fpiral canal by a plate coiled up within it like the main- 
fpring of a watch in its box ; only the fpires are at a dif- 
tance from each other, fo as to form a conduit of uniform 
width for the water. This fpiral partition is well joined 
to the two ends of the cylinder, and no water efcapes be¬ 
tween them. The outermoft turn of the fpiral begins to 
widen about three-fourths of a circumference from the 
end, and this gradual enlargement continues from Q to S 
nearly a femicircle; this part may be called'lhe horn. It 
then widens fuddenly, forming a /coop or (hovel S S'. The 
cylinder is fupported fo as to dip feveral inches into the 
water, whofe furface is reprefented by V V'. When this 
cylinder is turned round its axis in the dirertion ABEO, 
as expreffed by the two darts, the fcoop S S' dips at V', and 
takes up a certain quantity of water before it immerges. 
again at V. This quantity is fufneient to fill the taper 
part S Q, which we have called the horn; and this is. 
nearly equal in capacity to the outermoff uniform fpiral 
round. After the fcoop has emerged, the water palfes 
along the fpiral by the motion of it round the axis, and 
drives the air before it into the rifing-pipe, where it 
efcapes. In the mean time, air comes in at the mouth- 
ot the fcoop ; and, when the fcoop again dips into the. 
water, it again takes in fome. Thus there is now a part, 
filled with water, and a part filled with air. Continuing, 
this motion, we (hall receive a fecond round of water and. 
another of air. The water in any turn of the fpiral will 
have its two ends on a level, and the air between the fuc- 
ce/five columns of water will be in its natural ftate; for 
lince the paffage into the rifing-pipe, or main, is open,.there 
is nothing to force the water and air into any other pofi« 
tion. But, fince the fpires gradually diminilh in their 
length, it is plain that the column of water will gradu¬ 
ally occupy more and more of the circumference of each. 
At 1 alt it will occupy a complete turn of fome fpiral that 
is near the centre ; and, when lent farther in by the con¬ 
tinuance of the motion, fome of it will run back over the 
top of the fucceeding fpiral. Thus it will run over at K 4. 
into the right-hand fide of the third fpiral. Therefore it 
will pulh the water of this fpire backwards, and raife its 
other end, fo that it alfo will run over backwards before the 
next turn is completed. And this change of dilpolition 
will at laft reach the firft or outermoft fpiral, and fome 
vvater will run over into the horn and lcoop, and finally 
into the ciftern. But, as foon as water gets info the riling- 
pipe, and riles a little in it, it Hops the efcape of the air 
when the next fcoop of water is taken in. Here are now- 
two columns of water arting againlt each other by hy- 
drolfatic preffure and the intervening column of air. They 
mult comprefs the air between them, and the water and 
air columns will now be unequal. This will have a ge¬ 
neral tendency to keep the whole vvater back, and caufe 
it to be higher on the left or riling fide of each fpire than 
on the right or defeending lide. The excefs of height will 
be juft lucli as produces the compreflion of the air between 
that and the preceding column of water. This will go 
on increafing as the water mounts in the rifing-pipe ; tor 
the air next to the rifing-pipe is compreffed at its inner 
end with the weight of the whole column in the main. It 
mull be as much compreffed at its outer end. This muff 
be done by the water-column without it; and this column 
exerts this preffure partly by reafon that its outer end is 
higher than its inner end, and partly by the tranfmilfion 
of the preffure on its outer end by air, which is fimilarly 
compreffed 
