The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1841-10-22 00:00:00

IMPORTANT INVENTION IN MACHINERY

Our attention has been called, by an article in one of the
provincial newspapers, to a very important mechanical in-
vention, for which a patent has recently been granted to two
Scotch gentlemen, and which promises to effect a greater
and more beteficial change in the working of machinery than
has taken place since those most brilliant discoveries of Watt.
The two great drawbacks of the steam-engine (besides the
large space it occupies) have been the bulk, and the conse-
quent expense of the fuel which it requires—the latter pre-
venting its application to many purposes for which it would
otherwise have been a most effective agent; and the former
impeding its locomotive energy, and confining it, particularly
as regards navigation, within comparatively narrow lim ts.
Any reduction in either of these respects is thereby obviouisly
so much clear gain. The invention to which we allude pro-
mises to effect a prodigious saving in both, by diminishing
the expenditure of fuel to somewhat less than one-fifth of
what is now required for an equal degree of power. It has
already, we are informed, been put to the test by the con-
struction of an engine of about 20-horse power, which has
far some time been driving alt the machinery of an extensive
foundry with no larger consumption than we have just men-
tioned, and with every prospect of a considerably greater
reduction being effected by some slight changes in the details.
The motive power used is the common atmospheric air; and
another great advantage of the new engine arises from a
saving of space, equal to what is usually occupied by the fur-
nace and boilers of a steam-engine. If these things be so,
it is impossible to calculate the results to which so important
a discovery must lead. The following is a description of the
engine referred to :

The air-engine now working at the Dundee Foundry, for
which a patent was lately taken out, is the joint invention of
the Rev. Dr. Stirling, of Galston, and of his brother, Mr.
Stirling, engineer, of Dundee. The principle of the inven-
tion consists in alternately heating and cooling two bodies of
air confined in two separate vessels, which are so arranged,
that by the strokes of two plungers, worked by the engine,
the whole of the air contained in one of the vessels is sent to
the lower end immediately over the furnace, and is conse-
quently made quite hot, while the whole of the air contained
in the other vessel is at the same time transmitted to the
upper end, which is cut off from any communication with the
furnace, and is therefore comparatively cold. The expansion
caused by the heat renders the air in the one vessel alter-
nately much more elastic than that in the other ; and the
two ends of the working cylinder, which is fitted with a piston
similar to .that of. a steam-engine, being respectively con-
nected with the two air vessels, a preponderating pressure is
produced, by turns, on each side of the piston, which is
thereby pushed to the opposite end of the cylinder, and so,
by the alternate action of the plungers in the two air vessels,
it continues a reciprocating motion, and is applied to turn a
crank in the same way that a steam-engine does. It has
been satisfactorily shown that this engine may be worked
with very great economy of fuel as compared with a steam-
engine. The principal means of producing the saving
is this—that of the heat which is communicated to
the air from the furnaces, only a very small portion is
entirely thrown away when it conies again to be cooled ;
for. by making the air, in its way from the lint to the cold
end of the air-vessel, to pass through a chamber divided into
a number of small apertures or passages, the great extent of
surface with which it is thereby brought in contact, extracts
from it in the first place, but only temporarily, the greater
part of the heat, and afterwards restores it to the air on its
passage back again from the cold to the hot end of the vessel.
The process of cooling is finally completed, by making the
air pass through between a number of tubes in which there is
a current of cold water, and thus far the heat cannot be made
available again ; but the portion which is abstracted in this
way is very small. As a sufficient expansive power could
not be attained in so small a space without greater alterna-
tions of temperature from using air of the common density of
the atmosphere, the air used is pretty highly compressed,
and a much greater power is thereby obtained upon a given
area of the piston. A small air-pump, worked by the engine,
is therefore necessary to keep up the air to the requisite den-
sity ; but very little power is expended on this ; all that is re-
quired of the pump, after the engine has been once charged, be-
ing to supply any loss of air that may arise from leakage, which
is found to be very trifling. The machine has been working oc-
casionally for above six months, and it has been proved to be
capable of performing advantageously theamount of work which
the inventors had anticipated from their calculations and pre-
vious experiments. It has now for upwards of a month been
driving all the machinery at the extensive engineering works
of the Dundee Foundry, which a steam-engine of approved
e i
this invention must necessarily construction had hitherto been employed to do ; and it has
been ascertained that the expenditure of fuel is, cateris pa-
ribus, less than one-fifth part of what was required for the
steam-engine; but as considerable improvements are con-
templated in some of the details, it is confidently expected
that a much greater saving will eventually be effected. The
whole machine, including its furnaces and heating apparatus,
stands in about the same space that a steam-engine of equal
power would occupy without its furnaces and boiler. Taking
into account the saving of space along with the vast economy
of f
be of immense impor-
tancefor all ordinary purposes requiring motive power. As
an instance,
it would reduce the expense of the power em-
ployed in driving machinery in Dundee alone by at least
£25,000 or £30,000 a-year. But, viewed in reference to the
purposes of navigation, it must lead to results more extraor-
dinary, and will render a voyage to India round the Cape, by
machinery,
amatter of perfectly easy accomplishment.—
Journal. Mining

THE TEA TRADE—LONDON, MONDAY.—The market for
tea bas been steadier since this day week, and the public
sales have gone off much better than could have been antici-
pated, seeing the heavy supplies that have come in continually,
and the still larger quantities daily expected. Great difference
of opinion exists, swayed, no doubt, by interest in many
cases, as to the future range of prices; but as some of the
dealers unconnected with speculation have suffered their
-stocks to get very low, as a matter of prudence in the event
of any sudden change in the state of affairs at Canton, they
are obliged to come into the market as pirchasers forpresent
wants, and this prevents a fall in prices. The deliveries last
week amounted to 463,550 lbs., being an increase on the
previous fortnight.