MECHANICS. 
qTermiffion of the Board of Navigation, is Rationed be¬ 
tween London and Blackfriars bridges. Such grant was 
obtained with the laudable view of reducing, if poffible, 
the price of flour in the metropolis, and furnilhing a con- 
lfant fupply of that neceffary article of fubfiflence. The 
timplicity of this invention renders a long defcription fu- 
perfluons ; as it conlifts in merely applying the force of 
two or three water-wheels on each tide of a barge, or any 
fcnh-.r veflel better calculated to contain the interior part 
of the machinery. Were feveral mills of this kind to be 
ftationed on the Thames, or any other river where the 
tide ebbs and flows, there would doubtlefs be numerous 
advantages refult; for they would- be far leis expenfive 
than fleam-engines in the original ereffion, befides that 
they would lead to a confiderable annual faving in the 
important article of coals. 
t Of the STEAM-ENGINE. Plate XXIX. XXX. 
This is the name of a machine which derives its moving 
power from the elafticity and condenfibility of the fleam 
of boiling water. It is the moft valuable prefent which 
■the arts of life have ever received from the philofopher. 
The mariner’s compafs, the telefcope, gunpowder, and 
other molt ufeful fervants to human weakneis and inge¬ 
nuity, were the productions of chance, and we do not ex¬ 
actly know to whom we are indebted for them; but the 
fleam-engine was, in the very beginning, the refult of re¬ 
flection, and the production of a very ingenious mind ; 
and every improvement it has received, and every altera¬ 
tion in its conftruCtion and principles, were alfo the re¬ 
sults of philofophical ltudy. We may fay indeed, that 
the fleam-engine is that machine, perhaps, in which the 
genius of mechanifm has been manifefled in the higheft 
degree ; for no idea could be more happy than that of 
employing alternately, as moving powers, the expanlive 
force of the fleam of water, and the weight of the atmof- 
phere. Such indeed is the principle of this ingenious 
machine, which is at prefent employed with fo much fuc- 
cefs in pumping water from mines, and for a variety of 
other purpofes in the arts and manufactures. 
The firfl: part of this machine is a large boiler, to the 
cover of which is adapted a hollow cylinder, two, three, 
or four, feet in diameter. A communication is formed 
between the boiler and the cylinder by an aperture, ca¬ 
pable of being opened or (hut. Into this cylinder is fitted 
a piflon, the rod of which is made faft to the extremity 
of one of the arms of a working beam, having at the ex¬ 
tremity of its other arm the weight to be railed, which is 
generally the piflon of a fucking-pump, adapted to raile 
water from a great depth. The whole muft be combined 
in luch a manner, that, when the air or fleam has free ac- 
cefs into the cylinder, which communicates with the boiler, 
the weight alone of the apparatus affixed to the oppofite 
arm (hall be capable of railing that piflon. 
Let us now fuppofe the boiler filled with water to a cer¬ 
tain height, and that it is brought to a flate of complete 
ebullition by a large fire kindled below the boiler. As a 
part of this water will continually rife in fleam, when the 
communication hetw’een the boiler and the cylinder is 
opened, this vapour, which is elaltic, will introduce iti'elf 
into it, and raile the piflon ; as its force is equivalent to 
that of air. Let us fuppofe alio that the piflon, when it 
attains to a certain height, by means of fome mechanifm 
which may be eafily conceived, moves a certain part of the 
machine, which intercepts the communication between 
the boiler and the cylinder; and, in the laft place, that by 
the fame caufe a jet of cold water is thrown beneath the 
bottom of the piflon in the cylinder, fo as to fall down 
through the vapour in the form of rain. At that mo¬ 
ment the fleam will he condemned into water; a vacuum 
will be formed in the cylinder, and conftquently the pif- 
ton will.be then charged with the weight of the atmo- 
fphere above it, or a weight equivalent to a column of 
water of the fame bafe and 32 feet in height. If the piflon, 
for example, be 52 inches in diameter, this weight will be 
VOL. XIV. No. 1012, 
equal to 29,450 pounds; the piflon will confequently be 
obliged to defcend with a force equal to nearly 30,000 
pounds, and the other arm of the working-beam, if it be 
of the fame length, will aft with an equal force to over¬ 
come the refiflance oppofed to it. When the piflon has 
made this firfl flroke, the communication between the 
boiler and the cylinder is reftored ; the fleam of the boil¬ 
ing water again enters it; and, the equilibrium between 
the air of the atmofphere and the infide of the cylinder 
being re-eftablilhed, the weight of the apparatus affixed to 
the other end of the working beam defcends, and raifes 
the piflonj the fame motion as before is renewed ; the 
piflon again falls, and the machine continues to produce 
its effeft. 
This great difcovery has been afcribed by the Englifli 
to the marquis of Worcefter, and to Papin by the French ; 
but it is almofl certain, that about thirty-four years be¬ 
fore the date of the marquis’s invention, and about fixty- 
one years before the conftrudlion of Papin’s digefler, 
fleam was employed as the impelling power of a flamp- 
ing-er.gine by one Brancas, an Italian, who publifhed an 
account of his invention in 1629. It is extremely pro¬ 
bable, however, that the marquis of Worcefter had never 
feen the work of Brancas; and that the fire-engine which 
he mentions in his Century of Inventions was the refult 
of his own ingenuity. The advantages of fleam as an im¬ 
pelling power being thus known, the ingenious captain 
Savery (in 1699) invented an engine which raifed water 
by the expanlion and condenfation of fleam. Several en¬ 
gines of this conftruflion were actually erefted in England 
and France, but they were incapable of railing water 
from depths which exceeded 35 feet. The fleam-engine 
received great improvements from our countrymen New¬ 
comen, Beighton, and Blakey ; but it was brought to its 
prefent flate of perfection by Mr. Watt of Birmingham, 
one of the inoft accomplilhed engineers of the prefent age. 
Hitherto it had been employed merely as an hydraulic ma¬ 
chine for draining mines or raiflng water; but, in confe- 
quence of Mr. Watt’s improvements it has long been uled 
as the impelling power of almofl every fpecies of machi¬ 
nery. It is a curious circumftance, that the fleam-engine 
was not only invented, but has received all its improve* 
ments, in our own country. 
The princi-ples and manner of operation of the Hearn- 
engines of Savery, Newcomen and Cawley, and of Watt, 
may be underflood from the following brief explanations 
and remarks, which are meant as preparatory to the more 
detailed accounts of the machines themfelves. 
1. Let there be a fucking-pipe with a valve opening 
upwards at the top, communicating with a clofe veflel of 
water, not more than thirty-three feet above the level of 
the refervoir; let the fleam of boiling water be thrown 
on the furface of the water in the veflel, and it will force 
it to a height as much greater than thirty- three feet as the 
elaltic force of the fleam is greater than that of air ; and, if 
the fleam be condenfed by the injection of cold water, and 
a vacuum thus formed, the veflel will be filled from the re¬ 
fervoir by the preffure of the atmofphere ; and, the fleam 
being admitted as before, this water will alfo be forced up ; 
and lo on fucceflively. Such is the principle of the firfl: 
fleam-engine ereCted by Capt. Savery. 
2. If the fleam be admitted into the bottom of a hollow 
cylinder, to which a foiid piflon is adapted, the piflon will 
be forced upwards by the difference between the elaftic 
forces of Iteam and common air; and, the fleam being 
then condenfed, the piflon will defcend by the preffure of 
the atmofphere, and fo on lucceffively. This is the princi¬ 
ple of the fleam-engine firfl contrived by Mefirs. Newcomen 
and Cawley, of Dartmouth. This is fometimes called the 
atmofpherical engine ; and'is commonly a forcing-pump, 
having its rod fixed to one end of a lever, which is worked 
by the weight of the atmofphere upon a piflon at the other 
end, a temporary vacuum being made below it by fud- 
denly condenfing the fleam, that had been admitted into 
the cylinder in which this piflon works, by a jet of cold 
9 K. water 
