MECHi 
gines will raife more than 26,000 cubic feet of water 24. 
feet high for every hundred-weight of good pit-coal con- 
fumed by them. 
In confequence of the. great fuperiority of Mr. Watt’s 
engines, both with refpeft to economy and manageable- 
nefs, they have become of mod extenfive ufe; and in every 
demand of manufacture on a great fcale they offer us an 
indefatigable fervant, whofe ftrength has no bounds. The 
greateft mechanical project that ever engaged the atten¬ 
tion of man was on the point of being executed by this 
machine. The States of Holland were treating with 
MelTrs Watt and Boulton for draining the Haerlem Meer, 
and even reducing the Zuyder Zee; but the troubles in 
which that nation became involved put an end to the 
projeft. 
It would be employing time to very little purpofe to enu¬ 
merate the various projects which have been let up to rival 
Mr, Watt’s engine ; and, if we had not feen that the mo ft 
palpable abfurdities are not without patronage, not in en¬ 
gineering only, but in concerns of greater or lefs impor¬ 
tance, we fhouId not be able to account for the preference 
lhown to fotne of as immeritorious productions as have 
peftered the world at any age: but the misfortune of our 
country is, that we all are great mechanics and fage po¬ 
liticians ; and, while one engine is condemned on account 
of its complex conftruCtion, however eflential, others are 
celebrated for their fimplicity, however abfurd. 
We mult, however, redeem from this charge an engine 
invented by Mr. Jonathan Hornblower, near Briftol, on 
account of its fingularity, and the ingenuity and real lkill 
which appears in fome particulars of its conftruCtion. 
The following fhort defcription will fufficiently explain 
its principle, and enable our readers to appreciate its me¬ 
rit. A and B (fig. 123.) reprefent two cylinders, of which 
A is the largelt. A pifton moves in each, having their 
rods C and I) moving through collars at E and F. Thefe 
cylinders may be fupplied with (team from the boiler by 
means of the fquare pipe G, which has a flanch to con¬ 
ned it with the reft of the (team-pipe. This fquare part 
is reprefented as branching off to both cylinders, c and d 
are two cocks, which have handles and tumblers as ufual, 
worked by the plug-beam W. On the fore-fide (that is, 
the fide next the eye) of the cylinders is reprefented ano¬ 
ther communicating pipe, whole fedion is alfo fquare or 
redangular, having alfo two cocks a, b. The pipe Y, 
immediately under the cock b, eftablifhes a communica¬ 
tion between the upper and lower parts of the fmal) cy¬ 
linder B, by opening the cock b. There is a fimilar pipe 
on the other fide of the cylinder A, immediately under 
the cock d. When the cocks c and a are open, and the 
cocks b and d are ftuit, the lteatn from the boiler has free 
admiflion into the upper part of the cylinder B, and the 
(leant from the lower part of B has free admillion into the 
upper part of A ; but the upper part of each cylinder has 
no communication with its lower part. From the bottom 
of the great cylinder proceeds the edudion-pipe K, hav¬ 
ing a valve at its opening into the cylinder, which bends 
downwards, and is conneded with the conical condenfer 
L. This, however, was Hopped'by Watt’s patent; and 
the condenfation mult be performed as in Newcomen’s 
engine, or at leaft in the cylinder A. The condenfer 
is fixed on a hollow box M, on which ftand the pumps 
N and O for extracting the air and water; which laft 
runs along the trough T into a ciltern U, from which 
it is raifed by the pump V for recruiting the boiler, 
being already nearly boiling hot. Immediately under 
the condenfer there is a fpigot-valve at S, over which is a 
fmall jet-pipe, reaching to the bend of the edudion-pipe. 
The whole of the condenfingapparatus is contained in a 
ciltern R of cold water. A fmall pipe P comes from the 
fide of the condenfer, and terminates on the bottom of the 
trough T, and is there covered with a valve Q, which is 
kept tight by the water that is always running over it. 
Laltly, the pump-rods X. caufe the outer end of the beam 
to preponderate, fo that the auiefcent pofition of the beam 
N I C S. 78 3 
is that reprefented in the figure, the piftons being at the 
top of the cylinders. 
Suppofe all the cocks open, and fteam coming in copi- 
oufly from the boiler, and no condenlation going on in 
L; the fteam mult drive out all the air, and at laft follow 
it through the valve Q. Now ftuit the valves b and d, and 
open the valve S of the condenfer. The condenlation 
will immediately commence. There is now no preffure 
on the under fide of the pi Hon of A, and it immediately 
defcends. The communication between the lower part 
of B and the upper part of A being open, the fteam will 
go from B into the fpace left by the pifton of A. It muff 
therefore expand, and its elafticity inuft diminilh, and 
will no longer balance the preflure of the fteam above the 
pifton of B. This pifton therefore, if not withheld by 
the beam, would defcend till it is in equilibrio, having 
fteam of equal denfity above and below it. But it can¬ 
not defcend fo far; for the cylinder A is wider than B, 
and the arm of the beam at which its pifton hangs is lon¬ 
ger than the arm which fupports the pifton of B ; there¬ 
fore, when the pifton of B has defcended as far as the 
beam will permit it, the fteam between the two piftons 
occupies a larger fpace than it did when both piftons were 
at the tops of the cylinders. Its denfity, therefore, and 
its elafticity, diminilh as its bulk increafes. It is there¬ 
fore not a balance; for the fteam on the upper fide of B, 
and the pifton B, pulls at the beam with all the difference 
of thefe preflures. The flighted: view of thefubjeiSl muffc 
(how the reader, that, as the piftons defcend, the fteam 
that is between them will grow continually rarer and lefs 
elaftic, and that both piltons will pull the beam down¬ 
wards. Suppofe now that each has reached the bottom 
of its cylinder. Shut the cock <2 and the eduffion-coclc 
at the bottom of A, and open the cocks b and d. The 
communication being now eftablilhed between the upper 
and lower part of each cylinder, nothing hinders the coun¬ 
ter-weight from raifing the piftons to the top. Let them 
arrive there. The cylinder B is at this time filled with 
fteam of the ordinary denfity, and the cylinder A with an 
equal abfolute quantity of fteam, but expanded into a 
larger fpace. Shut the cocks b and d, and open the cock 
a, and the edu< 5 lion-cock at the bottom of A ; the con¬ 
denlation wall again operate, .and the piftons defcend. 
And thus the operation may bcrepeated as long as (team 
is fupplied ; and one full of the cylinder B- of ordinary 
fteam is expended during each working-ftroke. 
Let us now examine the power of this engine. It is 
evident, that, when both piltons are at the top of their 
refpedtive cylinders, the aftive preffure (that is, the dif¬ 
ference of the preffure on its two fides) on the pilion of 
B is nothing, while that on the pifton of A is equal to 
the full preffure of the atmofphere on its area. This, mul¬ 
tiplied by the length of the arm by which it is fupported, 
gives its mechanical energy. As the piltons defcend, the 
preflure on the pilton of B increafes, while that on the 
pifton of A diminilhes. When both are at the bottom, 
the preffure on the pifton of B is at its maximum, and 
that on the pilton of A at its mininum. Mr. Hornblower 
faw that this mult be a beneficial employment ot fteam, 
and preferable to the practice of condenling it while its 
full elafticity remained ; but he has not conlidered it with 
the attention neceflary for afcertaining the advantage with 
precifion. And we may add, that, it the condenlation is 
performed in the cylinder A, which it mult be unlefs 
with the permillion ot Watt and Boulton, the engine 
cannot be much fuperior to a common engine ; for much 
of the fteam from below B will be condenled between the 
piftons by the coldnefs of the cylinder A and this di¬ 
minilhes the downward preffure on A more than it in¬ 
creafes the downward prelfure on B. We learn however 
that, by confining the condenfation to a fmall pari of the 
cylinder A, Mr. Hornblower has erected engines clear of 
Mr. Watt’s patent, which are confiderably fuperior to 
Newcomen’s ; fo has Mr. Symington. 
We faid that there was much ingenuity and real (kill 
obfervable. 
