Another disadvantage is the unequal form into
which the cylinder and piston rod become worn after
having been some years in use.
This arises from

the varied speed at which they travel, and to their
not passing over all parts of the surface. We have
seen a piston rod in use full as much out of form as
that in the drawing, and cylinders nearly so. The
form of the piston rod arises from the parts 1, 2,
and 3, 4, being only partially drawn through the
stuffing box, consequently less rubbed than the
middle, which is drawn through at each stroke.
The decreased diameter in the middle of the rod
arises from the speed being greater there than at
other parts, (the cause of which we have explained)
and creates in consequence a greater wear.

2

The irregular wear of the cylinder is produced in the same man-
ner. The piston is not drawn through, but merely comes in contact,
or is partially moved through 5, 6, and 7, 8, whilst it rapidly passes
the middle, and therefore, in that part, it is more worn than at any
other.

The last inconvenience we shall notice, though it is by no means
the least, is, that the fly wheel is the constant and indispensable
accompaniment of the crank. This will appear evident from what
we have already stated.

Independent of extra cost, extra friction, and extra room, it be-
comes necessary to have two engines in steam boats, to obtain any
thing like a regular motion, and even this is far from regular. In
steam boats the two cranks are fixed upon the same axle as that on
which the paddles are placed. By this contrivance, when the crank
of one engine is passing the centre and has no power, the other is at
its greatest power, and thus aiding each other, something like an
equality is preserved: but this is irregular, as a variation still
takes place in the mean length of the two

levers. a c, and eb, represent two cranks,
the axle of which is c. a c is now passing
the centre, and therefore has no power,
whilst the other, cb, is at its greatest
power. The mean length of the lever,
therefore, is at d, or one half of cb; but
when the two cranks have made one eighth
of a revolution, as to cf, and cg, then
the line, fg, shews the mean power to
be at e; having varied from e d to c e.~

This irregularity being unaided by a fly wheel may probably account
for the vibration which we feel in many steam boats, and which
appears to proceed from some other cause than the reciprocation of
the parts. It should be observed that the impetus of the boat makes
the paddles act as a kind of fly wheel, because if they were suddenly

disengaged from the machinery they would continue to revolve of
themselves so long as the velocity of the stream was less than the
velocity of the boat, because then the stream acts like the current for
an undershot wheel. So long as the vanes continued to be driven
against the water, so long would the motion of the wheels be continued
in the same direction as that given by the machinery; therefore we
say, they are fly wheels of a peculiar kind; but still as the speed would
immediately decrease as they were disengaged from the machinery,.
from the yielding nature of the medium through which they pass, so
also would they vary in velocity as the mean power of the crank
increases or diminishes.

[To be continued.]

MESSRS. LEDSAM AND COOK'S PATENT,
FOR THE PURIFICATION OF coal gas.

THE improvements contemplated by the patentees, (Messrs. J.
F. Ledsam, and Benjamin Cook, of Birmingham) consist in the em-
ployment of common salt, and certain metals in solution, for the
purification of coal gas, in preference to lime and other earthy
substances heretofore employed for the same purpose; the following
are the processes described in the specification.

Muriate of soda, or common salt is to be placed in alternate
strata with the coal in the retort; or the salt may be mixed with the
coal previous to subjecting it to distillation; by either of these means
it is said, that the gas as it is generated or emitted from the coals,
will be immediately purified. The quantity of salt required will vary
according to the nature of the coal; the quality of the salt is imma-
terial, the refuse taken from the bottoms of the pans in the salt
works, answering the purpose effectually.

Another method is to pass the coal gas generated in the ordinary
way, through several layers of dry salt in a distinct vessel or chamber.
A third method is to pass the gas through a solution of common
salt in water.

A fourth, to pass the gas through a solution of silver, copper,
iron, zinc, or other metal, in nitric, or other acid.

A fifth, is to combine two or more of the above processes in the
purification of coal gas.

TO OUR READERS.

EVE'S NEW STEAM ENGINE. We are happy to have it in our power to
announce that a full Description of Mr. Eve's New Patent Steam Engine will
appear in our next.

Published by COWIE & Co. Booksellers, 60, Paternoster-row; and 24,
Fetter-lane, where Communications for the Editor (post paid) are to be
addressed.

Sold by GEORGE HEBERT, 98, Cheapside ;-SHERWOOD, GILBERT, & PIPER, Pater-
noster Row; SIMPKIN & MARSHALL, Stationers' Hall Court; JOSEPH CAPES, 111,
Fleet Street; and may be had of all Booksellers in Town and Country.

PRINTED BY COE AND MOORE, 27, old change, st. paul's.

SPECIFICATION OF THE PATENT

RECENTLY GRANTED TO JOSEPH Eve, late of the United States, But now of Liverpool,

FOR IMPROVEMENTS IN STEAM ENGINES. SINCE the first notice of Mr. Eve's improved Steam Engine, which appeared in the Liverpool Courier, in December last, we have been solicitous to lay a description of it before our readers; it is, therefore, with peculiar satisfaction that we are now enabled to submit a full account of this ingenious and interesting invention to their consideration.

As, however, the introduction of the whole specification, and all the illustrations, into one single number, would occupy so large a space, as to preclude the insertion of other matters of interest, we shall divide it into two parts.

"To all to whom these presents shall come, &c. &c. Now know ye, that in compliance with the said proviso, I, the said Joseph Eve, do hereby declare, that the nature of my said improved steam engine consists of five particulars.-1st. In the application of revolving cones to rotary engines, in the manner hereinafter described, for the purpose of compensating any loss by friction, and in the general arrangement of the various parts of the rotary engine hereinafter described. 2nd. In a steam generator so constructed of tubes, that the heat of the furnace shall cause the water to circulate constantly through the tubes, thereby preventing the steam from driving the water out of them, by which means the said tubes are less liable to burn out, or become oxidated.-3rd. In an arrangement of one or more revolving cock or cocks for the purpose of supplying the generator with water in lieu of the ordinary forcing pump.-4th. In a new safety apparatus, by which the elasticity of steam in boilers is ascertained by weights directly applied, instead of indirectly, as in the ordinary steel yard valve.-And 5th. In an arrangement of cogwheels with a compound engine, in such manner, that the steam, after having acted as high pressure, may be used as low pressure with greater effect, than in any engine now in use; and in further compliance with the said proviso, I, the said Joseph Eve, do hereby describe the manner in which my said invention is to be performed, by the following mechanical description of the various improvements constituting the same, reference being had to the annexed engraved figures, and letters marked thereon, which illustrate three modes of constructing my rotary steam engine.

"Fig. I presents an end section, fig. 2 a longitudinal section of the said engine on the simplest manner of construction. The same letters refer to similar parts in all the figures.

"a a are the cylinder and cone revolving in contact in opposite directions, the cone having one groove and being one third of the diameter of the cylinder, which latter has three wings or pistons ccc, the ends of which as they revolve, touch the outer case e, and do not admit any steam to pass. The steam is admitted through

the pipe f, and acting on the wing c, causes the cylinder to revolve until the said wing passes the pipe g, when the stratum of steam lodged between each two wings, is allowed to escape. The wing, which has thus passed, falls into the groove d of the cone, the bottom of which groove it touches in passing, thus allowing no steam to escape between. The said wing e then passes again by the steam pipe f, and is acted upon as before described, and so on in rotation. The cylinder d, which is firmly fixed to its axis b, rests on one side on the outer case e, through which the axis projects, but as there is some friction produced by the revolution of the said cylinder at its two ends touching the outer case, I have placed a false end h h under the opposite end of the cylinder, which false end slides on the axis b freely, and has a thread cut at the end, by means of which and the adjusting nut i, the cylinder, if worn at the two ends, can be easily tightened and adjusted. The adjusting nut is confined by the collar k, which collar is screwed to the outer case. The conical shape of the small runner, which can likewise be moved upwards or downwards in the outer case, serves to keep the two convex surfaces of the cylinder and cone in contact, so that no steam can escape between them. It is obvious from the conical shape of the runner, that, the longer the engine will be in use, the better it will work, and the more steam tight it will become.

The groove d in the conical runner is cut into a separate piece of metal, which slides by an adjusting screw o up and down, so that when the engine is adjusted, the groove d, on the piece of metal, into which the said groove is cut, can be moved up and down, so as to fit the wings of the cylinder.

"Letters n n in fig. 2 present two cog-wheels running into cach other, attached on the outside of the engine to the axis of the cylinder and cone, placed there for the purpose of producing a corresponding revolution of the said cylinder and cone, thus causing the groove of the cone to present itself regularly to the wings of the cylinder; o is a pinion fixed to the other end of the axis, by means of which any machinery can be put into motion.

"Another variety of constituting a steam engine on my principle is shewn by an end section view in fig. 5, and an external view in fig. 6. This engine has a cylinder with two small conical runners on each side, the said conical runners being of the same construction as before described, with one groove cut into each, and being one third of the diameter of the cylinder. There are two induction and two eduction steam pipes, and, although the engine may be, with the exception of the addition of one of the conical runners, exactly of the same size as the one first described, a double quantity of steam is requisite, and twice the power of the former engine is gained the steam enters through pipe ƒ a, and acts on the wing c, which after having passed pipe go where the steam escapes, falls into the groove d of the lower cone, and appearing at the induction steam pipe fb, is loaded again with steam pressure, which it discharges at the second eduction pipe go, and then enters the groove of the upper cone, after having passed which, it is loaded again at the first mentioned induction pipe. C 2