560 
STEAM ENGINE. 
to the steam condenser, or serves for the escape of steam. 
Fig. 8, represents an outside view of the piston : a, is the 
rod already described; c c, are packing rings, two on the 
upper side and two on the lower side. These rings press 
against the tube, e, in order to keep it steam-tight, so that no 
steam can escape through the longitudinal openings; d d, are 
two pieces of metal, screwed on at the top and base of the 
piston, to confine the packing rings. 
V. The high and low pressure combination. —A, fig. 1, 
is the furnace containing the steam generator or boiler: B, is 
the dome on the top of the steam receiver, with the steam 
pipe, C, and safety apparatus, M. D, is a cock upon pipe 
C, through which steam is admitted to the high-pressure 
engine, E. After having acted upon it, the said steam passes 
into the low pressure engine, F, constructed on Mr. Eve’s 
principle on a larger scale, so as to allow the steam to ex¬ 
pand, and then act upon it as low pressure: E and F, have 
pinion wheels of an equal pitch, gearing into a spur wheel, 
G; these wheels determine the power given to each engine 
by regulating their motion with reference to the power re¬ 
quired from each. The steam finds its escape at Z, into the 
condenser, H; the condensed steam or water runs through 
pipe, I, by its own gravity, towards the two revolving cocks, 
K, whence it is conveyed back to the feeding pipe in the 
steam generator. V, is an engine, constructed upon the plan 
explained under head I., having two induction and two 
eduction pipes, which engine serves as a pump in this parti¬ 
cular situation. Pipe, W, sucks the water from the well or 
river, and carries it into the refrigerator; X receives the water 
in the refrigerator, and carries it downwards; P is the bel¬ 
lows, fanning the fire by means of a band round the axle, Q, 
connected with two pulleys, R and S, or by any other con¬ 
trivance ; O is the valve and lever of the bellows, connected, 
by rod N, with the safety apparatus; T and U, are pulleys, 
connected by a band to give rotary motion to pump V; but 
many other contrivances may be used; L is a cock, which is 
only opened before the engine is set to work, in order that 
the air may be driven out of the pipes and condenser by the 
steam; the cock may then be shut, and the engine set to 
work; Y is a pipe leading from the safety apparatus to the 
condenser. If an engine, therefore, be so contrived, and the 
boiler once filled with water, the same water will answer tor 
working the engine, as long as all the pipes through which 
the steam and water circulate, are tight; or, at any rate, the 
loss of water will be very inconsiderable. 
The advantages supposed to attend these engines are thus 
summed up by the patentee:— 
“ It is presumed, in the first place, that from a steam gene¬ 
rator so small as the above-described, containing little water 
and steam, with the provision made in its construction 
against any danger, even were a rupture to take place, no 
danger could possibly happen to persons near the engine. 
“ It is also obvious, that the quantity of fuel consumed, 
will bear a proportion to the boiler or steam generator, and 
that, comparatively, very little can be consumed in so small 
a furnace as my steam generator requires. 
“Thereare no reciprocating parts, levers, fly-wheels, or 
valves, but simply two revolving parts; and, if I may so 
speak, the whole power of the steam is appropriated by the 
direct or first intention. The relative weight and bulk of 
this engine will require a few more words for elucidation. A 
more concentrated power in steam engines is attainable in 
two ways:—-the first is by using steam of great elasticity; 
thus, on Mr. Perkins’s plan, a cylinder, two inches in dia¬ 
meter, would be sufficient for a ten-horse power. The se¬ 
cond method of diminishing the dimensions of steam engines 
is, to increase their mobility ; that is, to give greater velo¬ 
city to the part or parts on which the steam acts. This, in 
all engines having reciprocating motions, is limited; for 
motion, alternately in opposite directions, requires a certain 
time, otherwise the whole power of the engine may be con¬ 
sumed by simply overcoming the inertia. Now it is certain, 
abstractedly considered, that as we increase the velocity of 
the piston, we may decrease the size of the engine; it fol¬ 
lows, therefore, from the above premises, that if we could 
conveniently make use of steam of 150 pounds to the inch, 
instead of mere atmospheric pressure, and have 150 strokes 
to the same engine instead of 15, we should require 100 
times the power; or, what is the object at issue, have the 
same power with an engine and generator in that proportion 
smaller. 
“ The first object, as regards high pressure, it will not be 
too much to concede, as it has been long ago practica’ly 
attained by Evans, and others. And, as to the velocity 
which this engine is calculated to admit of from its construc¬ 
tion, though not unlimited, it is certainly very great, much 
more than ten times that of reciprocating engines, and much 
greater even than that of rotary engines, that have recipro¬ 
cating parts. Thus, if these premises be correct, it cannot 
be too much to say that this engine ought to have the same 
power as the engines in common use, though of smaller 
dimensions; and that the weight will be reduced, not in 
proportion to the reduction of its superficial, but its cubic 
dimensions. 
“ The simplicity of the engine (the next desideratum), I 
conceive, cannot be well increased, as the engine itself con¬ 
sists of but two revolving parts. And lastly, as a result, the 
expense of erecting an engine of a given power, on the con¬ 
struction of the above, ought to bear a proportion to the 
diminution of its bulk and weight, and greater simplicity. 
“ The difficulty of availing ourselves of the advantage of 
using steam twice, that is, first as high pressure, and then in 
a condensing engine to any extent, is sufficiently apparent 
from the following considerations. It appears from Mr. 
Woolf’s experiments, that steam, heated to balance six 
pounds to the inch, will expand into six times the volume 
under atmospheric pressure; at 20 pounds to 20 times; at 
40 pounds to 40 times, and so on. Woiking with com¬ 
paratively so low. a pressure as 40 pounds to the inch, it 
would be found extremely inconvenient to use two engines 
whose capacities were as one to forty; and if not impossible, 
would appear ridiculous, if steam of 200 pounds elasticity, 
which is quite common in the United States, be used, as the 
second engine would have to be 200 times the capacity of 
the first, which, in this extreme case, would, at least, have a 
disproportionate appearance. All reciprocating engines, or 
those having reciprocating parts, will have to contend with 
this inconvenience; or, rather, can only avail themselves of 
a partial advantage from using high and low steam, as they 
have to work stroke for stroke. With my rotary steam en¬ 
gine the full benefit of this principle may be appropriated, 
as the engine that acts by high pressure may be made to re¬ 
volve as much faster than the first as to allow of the full ex¬ 
pansion of the steam before it is acted on, for the velocity 
may be carried to any extent required, without inconve¬ 
nience.” 
The application of the steam engine to navigation, and 
the earlier efforts that were made towards its improvement, 
are mentioned in the article Mechanics. As, however, the 
subject is not very fully entered into in that place, we shall 
give it some further notice here. In the first place, as to 
the inventor of the steam, there are some disputes. 
The method of propelling vessels by the action of wheels 
or paddles, instead of oars, is described in a very curious 
and learned treatise, Dc Re Militari, by Valturius, of Ri¬ 
mini, and first printed by John of Verona, in 1472. 
From this book it is clear that, three or four centuries ago, 
boats, propelled by the action of paddle-wheels, were used 
on some of the large rivers in Italy, and, most probably, in 
other parts of the continent, for the transporting of troops. 
Valturius even speaks of pontoons, composed of three parts, 
like drums, which could be conjoined at any time, and again 
separated, to facilitate their carriage over land. The method 
of changing a reciprocating into a rotatory motion, by the 
help of a crank, though not applied to the steam engine till 
50 or 60 years after its invention, had been understood and 
practised at the very dawn of the mechanical arts. 
The atmospherical steam engine, which had been invented 
by Newcomen and improved by Beighton, began to be pretty 
generally adopted in the coal-works, about the year 1720; 
and 
