1805.] 
ing with the expitfive force of four 
pounds the fquare inch, againft the fafety- 
valve, expofed alfo to the weight of the 
atmofphere, is capable of expanding itfe!f 
to four times the volume it then occupies, 
and fill to be equal to the preffure of the 
atmofphere ; fo, in like manner, fteam of 
the force of five pounds the fquare inch, 
can expand itfelf to five times its volume ; 
and quantities of fteam, of the like ex- 
paniive force, of fix, feven, eight, &c, 
pounds the {quare inch, can expand itfelf 
to fix, feven, eight, &c. times its volume, 
and ftill be capable of producing fufficient 
action againft the piftons of a fteam en- 
gine, to caufe it to rife in the old engine 
of Newcomen, or to be carried into the 
vacuous part of the cylinder in the im- 
proved engines ; and this ratio is progrel- 
five, aod rearly, if not intirely, uniform ; 
fo that fteam, the expanfive force of 
which is equal to twenty, thirty, forty, or 
itty pounds, the fquare inch of a common 
fafety-valve, will expand itfclf to twenty, 
thirty, forty, or fifty times its volume. — 
Upon this principle the patentee has found- 
ed his improvements, the defcription of 
which we fliall endeavour, by abridgment, 
to bring into a moderate compafs. 
An engine conftruéted upon’ Mr. 
Woolf’s plan muft have two tteam-vef- 
fels of different dimenfions, according to 
the temperature, or expanfive force, to be 
communicated to the fteam. Each fteam- 
veflel fhould be furnifhed with a pifton, 
and the fmaller cylinders fhould have a 
communication, both at top and bottom, 
with the boiler which fupplies the fteam, 
which communications, by means of 
cocks, or valves, are to be alternately 
opened and fhut during the working of the 
engine. The top of the fmall cylinder 
fhould have a communication with ihe 
bottom of the larger cylinder, and the 
bottom of the fmaller with the top of the 
larger, with proper means to open and 
fhut thefe al'ernately, by cocks, valves, 
&c.; and both top and bottom of the 
larger cylinder, or fteam-veffel, fhould, 
while the engine is at work, communicate 
alternately with a condenfing-veflel, iuto 
which a jet of water is admirted to haften 
the condenfation ; or the condenfing-vel- 
fel may be cooled by any other means cal- 
culated to produce that effect. When the 
engine is at work, fteam of high tempe- 
rature is admitted from the boiler, to act, 
by its elaftic force, on one fide of the fmal- 
ler pifton, while the team which had laft 
moved it has a communication. with the 
Jarger Ream-veflel, where it follows the 
larger pifton, now moving towards that 
New Patents lately enrolled. ! 53 
end of its: cylinder which 1s open to the 
condenfing-veflel. Let both piftons end 
their ftroke at one t'me, and fuppofe them 
both at the top of their refpeétive cylin- 
ders, ready todefcend, then the fteam, en - 
tering above the fmaller pifton, will carry 
it downwards ; while the {team below ir, 
inftead of being allowed to efcape into the 
atmofphere, or applied to any other pur- 
pole, will pafs into the larger cylinder, 
above its pifton, which will take its 
downward ftroke at the fame time that the 
pifton of the fmaller cylinder is doing the 
fame thing. When both piftons have 
been made to defcend to the bottom of 
their refpective cylinders, then the fteam 
from the boiler is. to be fhut off from the 
top, and admitted to the bottom of the 
fmailer cylinder, and the communication 
between the bottom of the {mailer and the: 
top of the larger cylinder is alfo to be cut 
off, and the communication to be opened 
between the top of the fmaller and the 
bottom of the larger cylinder; the fteam, 
which, in the downward ftroke of the en- 
gine, filled the large cylinder, being now 
open to the condenfer, and the communi- 
cation between the bottum of the larger 
cylinder and the condenfer fhut off 5 and 
fo alternately admitting the fteam to the 
different fides of the fimaller pifton; while 
the feam laft admitted into the fimaller 
cylinder paffes alternately to the different 
fides of the larger pifton, the top and bot- 
tom of which are made to communicate 
alternately with the condenter. 
Mr. Woolf is aware of the difficulty of 
giving to large cylinders a degree of 
ftrength fufficient to bear the aétion of 
very powerful fleam, and therefore he 
propofes to ufe two or more {maller cylin- 
ders in the place of the larger one; but 
the piftons of thefe mu& be made to a& 
together. He alfo propofes to improve 
engines already conitruéted, by adding a 
{mall engine, or meafure, for the fteam 
admitted to the working cylinder ; and, 
in the {pecification, rules are given for the: 
proper conitruétion of {uch improvements, 
which, we are told, may be readily intro- 
duced into Mr. Watt’s engines. He re- 
commends, that, in all cafes, the fmaller 
veflel flould be a meafure for the larger ; 
and, as an example, he advifes, if fteam of 
forty pounds the {quare inch be fixed on, 
then the {maller fteam-veffel fhould be at 
leaft one-fortieth part of the contents of 
the larger one ; or one thirtieth, or one- 
twentieth, when fieam of thitty or twenty 
pounds the fquare inch is to be ufed.— 
Thefe, however, are not the only propor- 
tions that may be uted with fatety, and 
even 
