7 c?4 M E C H 
obfervable in many particulars of this engine. The dif- 
pofition and connexion of the cylinders, and the whole 
Conden'fing apparatus, are contrived with peculiar neat- 
nefs. The cocks are very ingenious ; they are compofed 
of two flat circular plates ground very true to each other, 
and one of them turns round on a pin through their cen¬ 
tres; each is pierced with three feftoral apertures, exaft- 
ly correfponding with each other, and occupying a little 
lefs than one-half of their furfaces. By turning the move- 
able plate fo that the apertures coincide, a large paflage 
is opened for the fleam; and, by turning it fo that the 
folid of the one covers the aperture of the other, the cock 
is (hut. Such regulators are now very common in the 
caft-iron (loves for warming rooms. Mr. Hornblower’s 
contrivance for making the collars for the pifton-rods 
air-tight is alfo uncommonly ingenious. This collar is 
in faft two, at a fmall diflance from each other. A fmall 
pipe, branching off from the main fleam-pipe communi¬ 
cates with the (pace between the collars. This fleam, be¬ 
ing a little ftronger than the preflure of the atmofphere, 
effectually hinders the air from penetrating by the upper 
collar ; and though a little fleam fhould get through the 
lower collar into the cylinder A, it can do no harm. We 
fee many cafes in which this contrivance may be of fig- 
lial fervice. But it is in the framing of the great work¬ 
ing-beam that Mr. Hornblower’s fcientific knowledge is 
mod confpicuous; and we have no hefltation in affirming 
that it is ftronger than a beam of the common form, and 
containing twenty times its quantity of timber. There is 
hardly a part of it expofed to a tranfverfe drain, if we ex¬ 
cept theftrain of the pump V on the ftrutt by which it is 
worked. Every piece is either puflied or pulled in the 
direction of its length. We only fear that the bolts which 
conneft the upper beam with the two iron bars under its 
ends will work loofe in their holes, and tear out the wood 
which lies between them. We would propofe to fubfti- 
tute an iron bar for the whole of this upper beam. This 
working-beam highly deferves the attention of all carpen¬ 
ters and engineers. 
We (hall here notice another engine of Mr. Horn¬ 
blower’s, for which letters patent have been lately granted, 
having a rotary motion within itfelf by the immediate 
aftion of fleam on four revolving' piftons. The piftons 
juft mentioned are four vanes like thofe of a fmoke-jack, 
though not of thin iron, but of pretty confiderable thick- 
nefs, fufficient to form a groove to hold fome fluffing for 
the purpofe of being tight in their aftion. They are 
mounted on an arbor, which has a hollow nave in the 
middle. Into this nave the tails of the vanes are inferted, 
and each oppofite vane is affefted alike by having a fteady 
connexion with the other. For inftance, if we fhoukl 
alter the angle of one of the vanes with the arbor, the op¬ 
pofite one will be altered too ; and they are not fet in the 
fame plane, but at right angles to the plane of each other ; 
fo that, if we (in retaining the notion of the vanes of a 
fmoke-jack) conceive thefe vanes to be held in a vertical 
pofition like the fails of a windmill, when one vane is flatly 
oppofed to the wind, the oppofite vane will prefent its 
edge to the wind ; and this they are conftantly doing in 
their rotation on their common arbor, fo that the fleam 
afts againft the vane on its face in propelling it into ac¬ 
tion ; and this it does for about £ of a circle, or 90 de¬ 
grees, in the box where it is deftined to aft ; and, as foon 
as it has gone through the quarter of the circle, it in- 
ftantiy turns its edge to the fleam, while at the fame in- 
flant another vane has entered the working part of the 
box, and the rotation proceeds without interruption. It 
muff be obferved, that, though the engine has the power 
of prefenting the edge of the vanes to the fleam in return¬ 
ing to its place of aftive force, yet there muft be fome 
power loft according to the re-attion on the thicknefs of 
the edge, and this lofs of power is greateft only in fmall 
engines; but in a lyflern of vanes extending five or fix 
feet, moving at the rate of thirty revolutions in a minute, 
there muft be a great accumulation of force ; and that this 
accumulation is in favour of the principle of the engine. 
A N I C S. 
where the velocity of the power may be of any determinate 
ratio to the velocity of the weight, according to the exift- 
ing circumftances. It muft alfo be underflood that this 
engine is to be furnifhed with a condenfer and difeharging- 
pump, according to the new mode of condenfation efta- 
hlifhed by Mr. Watt; hut Mr. Hornblower has (as we 
think) an improved method of difcharging, whereby he 
takes all the air from the condenfer in a mod perfeft 
manner. This apparatus is to be connefted to one end 
of the arbor which carries the vanes or piftons, while the 
other end is connected with the work. 
Fig. 124.. is the plan or horizontal feftion of the en¬ 
gine ; where A AAA is the exterior box or cafing ; B C 
two of the vanes; C prefenting the whole furface of one, 
and B fhowing the edge of the other ; pppp forms an en¬ 
tire partition ; fo that all the communication between the 
upper and nether parts of the box are at B C ; D is the 
nave through which the vanes are connected, and O O is 
the arbor. Fig. 125. is a vertical feftion through the fame 
line; C and B (how the fame vanes as before; the nave 
in the middle is open to (how how the two vanes are con¬ 
nected. Another two, being connnefted in the fame man¬ 
ner, will have liberty to turn a quarter round without ob- 
ftruftion by the crooked part of the communicating axis ; 
this is the fleam-pipe, and the exhaufting-pipe nray be 
placed any-where above the partition. 
Mr. Gregory, while he refpefts the practical talents of 
the inventor of this engine, ftates his apprehenfions that 
it may not be found in practice to poflefs all the advan¬ 
tages which at fil'd view one would be inclined to aferibe 
to it. Is there not fome ground to fear that in this con¬ 
trivance, fiefides the force loft by the aftion of the fleam 
upon the edges of the vanes, there will be a confiderable 
lofs ariling from the greater friftion attending its opera¬ 
tions than thofe of a common fleam-engine ? In this 
fleam-wheel there will be a great quantity of rough fur- 
face (that of the fluffing) expofed to frequent contaft, and 
confequent refiflance to the moving from the fixed parts. 
Befides, as the fluffed parts are here of great extent with 
regard to the magnitude of the machinery, and exhibit 
rapid variations of fliape, they may, when brought into 
conftant work, be found difficult to keep in order. Whe¬ 
ther the difadvantages which may arife from thefe caufes, 
may be as great as thofe that are known to attend the 
other engines,and particularly whether they will be equi¬ 
valent to the force abforbed by giving a new impulfe to 
the whole mafs of matter fubjeft to the reciprocating mo¬ 
tion at every change in the direction, can only be fatif- 
faftorily afcertained by fubjefting both engines to com¬ 
parative work in as nearly the fame circumffances as the 
difference in conftruftion will admit. But, if by further 
attention to this ingenious contrivance, Mr. Hornblower 
(hould be able to work his fteam-wheel in a manner free 
from any material drawback upon the advantage arifing 
from its conffant rotary motion in one direction, it 
would then undoubtedly be fuperior to any fleam-engine 
of which we have ever heard, or that has probably been 
yet invented. 
Before we quit the fubjeft of fleam-engines, we (hall 
prefent the reader with fome account of the late improve¬ 
ments in their conltruftion, &c. by Mr. Arthur Woolf. 
Mr. Woolf founds his improvements on a very im¬ 
portant difeovery which he has made refpefting the ex- 
panfibility of (team when increafed in temperature beyond 
the boiling point, or 212 0 of Fahrenheit’s thermometer. 
It has been known for fome time, (and for this difeovery 
the world is indebted to Mr. Watt, the principal improver 
of the (team-engine,) that fleam, afting with the expanfive 
force of four pounds the fquare inch againft a fafety- 
valve expofed to the atmofphere, is capable of expanding 
itfelf to four times the volume it then occupies, and Hill 
to be equal to the prdlureof the atmofphere. Mr. Woolf 
has difcovered that, in like manner, fleam of the force of 
five pounds the fquare inch can expand itfelf to five times 
its volume ; that mafles or quantities of fleam of the like 
expanfive force of fix, feven, eight, nine, or ten, pounds 
1 the 
