556 
STEAM ENGINE. 
inventor of the steam engine. Nine years after Savery’s pa- inches, with a pressure initially of about 430 pounds on each 
tent he published an account of his invention, in a tract, square inch, that is, about 1300 pounds in the whole, or 
entitled “ Ars nova ad aquam ignis adminiculo efficacissime probably somewhat less, since the valve of the generator 
elevandum .”—“ A New Method of raising Water by the cannot be supposed to remain open long enough for the 
Force of Fire,” printed at Cassel, 1707. This machine, pressure on each side of it to become equal. The danger 
which is described in Belidor’s “ Architecture Hydrauhque,” of explosion, which has hitherto prevented the general 
vol. ii., does not essentially differ from that of the Marquis employment of engines with very high pressures, is here 
of Worcester, but is far less perfect than Savery’s: it works avoided by the great strength and the moderate dimensions 
wholly by the repellent power of steam : the only advantage 
is, that the receiver being made cylindrical, the steam is se¬ 
parated from the cold water by a floating piston, and that 
the water is made to flow in some degree constantly, by 
being thrown into a large air-vessel. In this publication, 
Papin admits that he had seen a draft of Savery’s engine, 
but says, that in the year 1698 he made a great number of 
experiments, by order of his serene highness Charles, Land¬ 
grave of Hesse, in order to raise water by the force of fire, 
which he communicated to several persons, and particularly 
to M. Leibnitz, who answered, that the same thought had 
occurred to himself. He also acknowledged that Captain 
Savery was about that time working upon the same subject 
in England, and that Savery had first published the fruit of his 
researches; that from 1698 the affair had lain dormant till 
the year 1705, when he received a letter from M. Leibnitz, 
then in London, which contained a draft of Captain Savery’s 
engine, and desired Papin’s opinion upon it. On shewing 
this draft to the landgrave, he ordered Papin to resume the 
work, and perfect the inventions which he had begun ; and 
which Papin then published, not with a view to make it 
supposed that Captain Savery had taken the thoughts from 
him, but to shew the world its obligation to the landgrave, 
in having first formed a design so useful, and in having 
brought it to its present degree of perfection; and he labours 
much to shew that his engine is preferable to that of Captain 
Savery. Although we must allow Dr. Papin to compliment 
his patron and himself upon Ihe success they met with, after 
encountering many unforeseen difficulties and experiments, 
which succeeded, as he tells us, quite contrary to their 
expectations, yet it cannot be allowed that Papin’s experi¬ 
ments in 1698 were the first, because the Marquis of Wor¬ 
cester’s publication was earlier by no less than thirty-five 
years: nor were they probable to have been so early as Sa¬ 
very’s beginning, since we cannot suppose that he would be 
at the expence of a patent, without some previous experi¬ 
ments to confirm his speculation, or that he could bring his 
engine to the degree of perfection in which he exhibited it 
to the Royal Society on the 14th of June, 1699, in less than 
a year, at a period when workmen were not ready or skilful 
in the execution of such machines as they now are in this 
country. 
The various improvements on Savery’s engine made by 
B/akey and others, will be found under the article Me¬ 
chanics, whereto the reader is also referred for the inven¬ 
tions of Newcomen, Fitzgerald, A. Woolf, James Watt, 
and Hornb/ower. Numerous have been the attempts since 
that period to improve the construction of the steam 
engine, but until the year 1823, no very great change was 
introduced. In this year appeared Mr. Perkins’s steam 
engine. 
This invention, as described in the Edinburgh Philoso¬ 
phical Journal for July 1823, appears to consist in substi¬ 
tuting for the boiler a strong vessel of gun metal, which he 
very properly calls a generator, intending to subject the 
water to a heat of between 400° and 500°, and allowing it 
1 o escape only through a valve loaded with a weight equi¬ 
valent to 35 atmospheres, while it is furnished with a safety 
valve loaded to 37, and with a gauge indicating, by means of 
a portion of compressed air, the actual pressure of the steam 
produced by it; and even the water that returns to the 
generator is subjected to a pressure of five or six atmospheres, 
which keeps it at a temperature of more than 300°. The 
generator contains eight gallons of water, or 2352 cylin¬ 
drical inches, while the piston is two inches in diameter, and 
the cylinder 18 inches long* containing 72 cylindrical inches, 
or j’, as much as the generator: affording a stroke of 12 
of the apparatus ; and besides the safety valves, a thin hall 
of copper, or a safety bulb, is provided, which will only 
sustain the pressure of 1000 pounds on the square inch, 
while every other part of the vessels is calculated to sustain 
4000. 
Mr. Perkins’s mode of applying heat to the water appears 
in reality to be extremely advantageous, not so much from 
any evidence that has been produced respecting the per¬ 
formance of the engine, as from the fact asserted by the 
writer in the Journal, that “as much low pressure steam, 
of four pounds on the square inch, may be generated by 
one bushel of coals,” employed upon three tubes of gun 
metal, communicating, by means of a loaded valve, with 
the boiler of a common engine, as by nine bushels applied 
in the ordinary manner. It has been conjectured that the 
heat is more easily communicated by the generator to the 
water, on account of the more intimate contact which sub¬ 
sists between them, and the absence of any nascent bubbles 
of steam in the neighbourhood of the common surface : but 
it appears to be more probable, that by far the most material 
part of the advantage depends upon the more perfect com¬ 
bustion of the coal at a high temperature near the external 
surface of the thick boiler: for it has been sufficiently 
proved by Sir. Humphry Davy and others, that an intense 
combustion evolves a much greater quantity of heat from 
the same materials than a more languid oxygenization. 
The quantity.of water, thrown out at each stroke, appears, 
from the table of densities inserted in this article, to be of 
the quantity that you will fill the cylinder, that is ^ of the 
content of the generator, and its conversion into steam at 
any temperature would not require, at the utmost, more than 
940° of heat, that is, a quarter of a degree for the whole of 
the water in the vessel, and possibly not above one-fifth 
of a degree. 
Numerous projectors have endeavoured to alter or im¬ 
prove the construction of the present steam engine; but 
though eonsiderab’e improvements have taken place in 
minor details, and in accurately determining the relative 
proportions of the different parts, no important and general 
improvement on the engines previously described has been 
effected. We speak here strictly of the steam engine; for, 
of late, a new era has been constituted in science by the in¬ 
troduction of other gaseous fluids than steam, as prime- 
movers.—Such engines ought, however, more properly to be 
called vacuum engines; a term, indeed, which would also 
include the majority of steam engines. As, however, the 
subject is mentioned, we shall not wait till our alphabetical 
arrangement brings us to that term, but shall introduce here 
what we have to say concerning these new instruments of 
motion. 
The experiments of Mr. Farrady and Sir H. Davy, in 
which the condensation of gases into liquids was effected, 
led to the formation of the first gas engine. That able 
engineer, Mr. Brunei, was the inventor of it. The gas he 
used, was the carbonic acid; and the following is the struc¬ 
ture of his engine :— 
It consists of five distinct cylindrical vessels (see fig. ], 
PL II.) The two exterior vessels, a and 5, contain the 
carbonic acid reduced to the liquid form, and are called the 
receivers; from these it passes into the two adjoining vessels, 
c and d, termed expansion vessels; these last, having tubes 
of communication with the working cylinder, e, the piston 
therein (shown by dots) is operated upon by the alternate 
expansion and condensation of the gas, giving motion to the 
rod, f and consequently to whatever machinery may be 
attached thereto. 
As the working cylinder, e, is of the usual construction, 
no 
