The former part of the APPENDIX, containing Tables of the Solidities and Superficies of Spheres, is also divided into three parts.

PART FIRST Contains Tables of the Solidities and Superficies of Spheres, whose Diameters are from One Inch to Twelve Inches, advancing by an Eighth.

PART SECOND Contains Tables of the Solidities and Superficies of Spheres, whose Diameters are from One Foot to Twelve Feet advancing by an Inch; from which Tables may also be known the Solidities and Superficies of Spheres, whose Diameters are from the Integer Twelve to One Hundred and FortyFour.

PART THIRD contains Tables of the Solidities and Sperficies of Spheres, whose Diameters are from the Integer One to Twelve, advancing by a Tenth. These are succeeded by

TABLES, containing the Areas and Diagonals of Squares, the Lengths of whose Sides are from One Inch to Twenty-Eight Inches, advancing by an Eighth; which Diagonals are, of course, equal to the Diameters of Circles whose Circumferences will just circumscribe the Angles of their corresponding Squares.

TABLES of the Specific Gravities of Bodies, in which the Weight of a Cubic Foot is given in Ounces and Pounds; the Weight of a Cubic Inch in Ounces; and the Number of Cubic Inches in a Pound, of each Body; all calculated to Avoirdupoise Weight.

There are also added to the pages

HEAD LINES, Containing the common Fractions of an Inch, (viz. Eighths) reduced to Decimals; the Common Fractions of a Foot (viz. Inches), reduced to Decimals; the Number of Cubic Inches in One Cubic Foot; the Number of Square Inches in One Square Foot; the Number of Cubic Inches in One Gallon of Ale; and the Number of Cubic Inches in a Gallon, Imperial Standard.

N. B.-The foregoing Paper had been lying at our Printer's, "set up in type," for more than a month, the pressure of other matter having prevented its insertion. In the interim Mr. George Hebert, of 88, Cheapside, has, we understand, become the Publisher of the Work, where it may be procured.]

History of the Steam Engine,
CHAPTER IV. continued.

BRAMAH AND DICKINSON'S ROTATIVE MOTION.-MR. JAMES SADLER'S ROTATIVE
ENGINE. CARTWRIGHT'S PISTON.

The following diagram represents another method by which Messrs.
Bramah and Dickinson proposed to obtain a rotative motion. A is a
smaller wheel or cylinder, armed with cross sliders, fixed in a larger
one B, but, instead of its axis being stationed in the centre of B, as
in the previous instances, it is moved as much eccentric as to cause the
periphery of A to rub against the side of B, as at C; this causes the
channel or groove DDD, to be formed of the shape which appears
in the figure. The inner surface of the wheel or ring B is not per-
fectly cylindrical, but is a curve of such a shape as would be described
by the points of the sliders EF being of equal length in the revo-
lution of the wheel A; or in other words, of such a shape as would
occasion all the four points of the said sliders to be in constant
The dotted lines GG show two grooves or
contact therewith.
cavities, through which the water, steam, or other fluid, contained
between the point C and either of the apertures of the pipes H and I,
passes into either of the said pipes; which water, steam, or other
fluid, would otherwise be pinned up by the slider, and stop the motion
of the machine when turned in either direction.*

*Repertory of Arts.

This machine would be liable to the same objections as the first. On the whole these contrivances display great ingenuity, and may be justly considered to rank as high as any that have since been proposed: indeed, there are few rotative engines which do not, in principle, somewhat resemble these: therefore we conclude that, had the genius of the inventor or inventors been exercised when mechanical experience had been more advanced, they might in all · probability have effected that which is so great a desideratum among modern engineers.

Mr. James Sadler, of Oxford, in 1791, obtained a patent for a Rotative Engine, which the following drawing and description may serve to illustrate. The steam generated in the boiler is conveyed through the pipe c, into the spindle or axis of the rotative cylinder ab, which is made steam-tight by working in a stuffing-box. The steam passes along the arms of the revolving cylinder, nearly to its ends, where it meets a jet of cold water, introduced from the hollow axis by the small pipe; this condensing water falls from the revolving cylinder into the bottom of the case, whence it is conveyed through a pipe, and is discharged by openings made in the ends or sides of another cylinder moveable in a horizontal direction, giving it a rotatory movement in the same manner as Barker's mill. The jet of cold water from the pipes xx, having condensed the steam, produces a re-action, and the cylinder a 6 acquires a rotative movement. The inner case is steam-tight; and the outer case serves the same purpose with the jacket in the reciprocating engines. Another mode of action is suggested by Mr. Sadler to be had by filling the case (in which the arms revolve) with steam, which would cause them to revolve by the pressure it would produce in being condensed in entering the arms.

This engine is Hero's in another form. That a patent should have been taken out for such an ineffective toy is a proof of great ignorance and inexperience.

The Rev. Edward Cartwright's scheme, for which he obtained a patent in 1797, was very ingenious. His object was to procure a tight piston and a condenser, in which the steam was exposed to a large surface of water.

The condensation is effected by two metal cylinders, placed one within the other, and having cold water flowing through the inner one, and enclosing the outer one. Thus the steam is exposed to the greatest possible surface in a thin sheet. Mr. Cartwright likewise has a valve in the piston, by which a constant communication is kept up between the cylinder and condenser, on either side of the piston, so that the condensation is always taking place, whether in the ascending or descending stroke. By this contrivance, steam that may escape past the piston will be immediately condensed, and the vacuum thereby preserved. This was considered to be a decided advantage over the general mode of arranging the valves, which does not always provide for the restoration of a vacuum destroyed by the imperfection of the packing.

"The piston b moving in the cylinder a, has its rod prolonged downwards; another piston d is attached to it, moving in the cylinder c, and which may be also considered as a prolongation of the steam cylinder. The steam cylinder is attached by the pipe g to the condenser, placed in cold water, formed of two concentric circular vessels, between which the steam is admitted in a thin sheet, and is condensed by coming in contact with the cold sides of the condensing vessel. The water of condensation falls into the pipe e. To the bottom of the cylinder i, a pipe m is carried into a box n, having a float-ball o, which opens and shuts the valve p, communicating with

the atmosphere: a pipe q is also fitted to the box. There is a valve placed at i, opening into the cylinder c; another at n, also opening upwards. The pipe s conveys steam from the boiler into the cylinder, which may be shut by the fall of the clack r. k is a valve made in the piston b.

from bote aida ai botsins of musta.ous dolly nosod alon "In the figure the piston b is shewn as descending by the elasticity of the steam flowing from the boiler through s: the piston d being attached to the same rod is also descending. When the piston breaches the bottom of the cylinder a; the tail or spindle of the valve

being

pressed upwards, opens the valve, and forms a communication between the upper side of the piston and the condenser; at the same moment the valve is pressed into its seat by the descent of the cross arm on the piston, which prevents the further admission of steam from the boiler; this allows the piston to be drawn up to the top of the cylinder, by the momentum of the fly-wheel z, in a nonresisting medium. The piston d is also drawn up to the top of c, and the valve iis raised by the condensed water and air which have accumulated in e, and in the condenser g. At the moment when the piston has reached the top of the cylinder, the valve k is pressed into its place by the pin or tail striking the cylinder cover; and at the same time the piston 6 striking the tail of the valve r, opens it; a communication is again established between the boiler and piston, and it is forced to the bottom as before. By the descent of the piston d, the water and air which were under it in the cylinder c, being prevented from returning into the condensing cylinder by the the valve under i, are driven up the pipe m, in the box n, and are conveyed into the boiler again through the pipe g. The air rises above the water in a; and, when by its accumulation its pressure is increased, it presses the float o downwards; this opens the valve p, and allows it to escape into the atmosphere."

This most ingenious machine, it appears, was tried first at Cleveland Street, Mary-le-bonne, and afterwards at Horsleydown, at both of which places it is said to have given great satisfaction. These trials must have been much more decisive than any opinion; and although we have not been able to ascertain further respecting the success of the engines when put in practice, than the simple fact of their having been approved of by the respective proprietors, our own judgment warrants a conclusion, that this plan is admirably adapted to be applied where a small engine is necessary. The objection against the mode of condensation adopted by Mr. Cartwright, was subject to great objection previous to experiment; so much so, that one of the greatest engineers this country ever produced, was heard to state it as his opinion, that "were a pipe to be laid across the Thames, the condensation would not be quick enough to work a steam engine with its full effect." It was shewn, however, when tried, that this opinion was incorrect, as the condensation was very rapid, and the vacuum tolerably good.

(TO BE CONTINUED.)

NEWCASTLE (Upon Tyne) MECHANICS' INSTITUTION.

We learn with much satisfaction from the Newcastle and other Provincial Papers, that Mr. E. Galloway, the Civil Engineer, and author of the History of the Steam Engine, now publishing in this Work, is at present engaged in giving a gratuitous Course of Lectures on that proudest and most interesting of subjects in practical science, the Steam Engine, which he illustrates by numerous working