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where they are piled or built up on a slider, so as to form lines. A very ingenious counting apparatus is applied to this part of the machine, for the purpose of indicating, by means of a dial in front-not the number of types in the receiver, but the actual space occupied by them, and consequently the space that requires filling up. When the line is completed, it is pushed out of the receiver into what is termed a justifying stick, where it is "read," and any errors corrected by an assistant compositor; after which, it is lowered into a galley.

It would be impossible to give more than a general notion of these machines, without the assistance of drawings; we have therefore confined ourselves to this hasty notice of their capabilities, and from the sometimes unwilling confession of printers, who have seen the machines at work, as to the practicability of now composing and distributing type by machinery, we should augur that a complete revolution in this branch of the arts, must inevitably take place.

The facility which the composing machine possesses, of delivering type into the receiver, is truly surprising. It has been proved, when the keys were played on at random, to clear out four hundred and fifty letters per minute, thus proving, that the capability of the machine's working, will be commensurate with the skill of the workman employed upon it.

Our reason for giving this early notice of the invention, is to bring immediately before the public an improvement which, we are convinced, will bear comparison in usefulness with any yet recorded in this work.

Scientific Notices.

REPORT OF TRANSACTIONS OF THE INSTITUTION OF CIVIL ENGINEERS.

(Continued from page 220, Vol. XXI.)

"Results of a Trial of the Constant Indicator upon the Cornish Engine, at the East London Water-works."

By Professor Moseley, F.R.S., &c.

The object of this communication, is to exhibit and explain the results given by the author's Indicator, during a continuous

registration from the 28th January to the 25th February 1842, the engine during that time making 232,617 strokes. The numbers registered by the counter of the engine and the Indicator, were noted each morning and evening, and are recorded in a table appended to the paper. The differences between each two consecutive numbers registered by the counter, giving the number of strokes made between each two observations, are contained in one column of the table, and in another column are the differences between the successive registrations of the Indicator. These are followed by the mean registrations of the Indicator at every stroke of the engine, being the quotients of the numbers in the last-named column, divided by the corresponding numbers of the preceding column. The paper, after thus stating the numbers registered daily by the Indicator, during the period of trial, proceeds to explain the formula, to which they are to be applied, in order to determine the work done daily by the engine. The formula, when reduced from the general one, by the introduction of the numerical values of the constants dependant upon this engine, is— U161.4474 N·09051 L.

In this expression, U, represents the units of work (in lbs. raised one foot high) done upon each square inch of the piston through any given time, during which the number, registered by the Indicator, is represented by N, and the space in feet, which the piston traverses, by L. The second term of the formula, which is very small as compared with the first, is a correction, for the influence of the friction of the Indicator, on the number registered by it. The formula being then reduced by the substitution in it of the numerical values before alluded to, the whole number of units of work, per square inch, of the piston, done between the 28th January and the 25th February, is shown to have been 21,464,067-1727. From this is deduced the work done, during the same time, upon the whole area of the piston, as well as the duty done upon the piston for each cwt. of coals. These calculations are followed by a comparison of the results given by the Indicator, with those previously obtained from actual experiment, by Mr. Wicksteed; whence it appears, that with a necessary allowance for a difference in the lengths of stroke at

the periods of the two experiments, the results of the two are almost coincident. The work, per stroke, upon every square inch of the piston, as obtained by experiment, is 120.574, whilst, as shown by the Indicator, it is 119.338 lbs.

Professor Moseley exhibited the Indicator, and described its construction and action. It consists of two cylinders, each four inches long, communicating by pipes with the top and bottom of the cylinder of the steam-engine, to which the instrument is applied. In each of these cylinders there works a solid piston, four square inches in area; both being fixed upon the extremities of the same rod, which (when the Indicator is in action) sustains, in the direction of its length, a pressure equal to the difference between the pressures upon the two Indicator pistons, or equal to the effective pressures of the steam on four square inches of the piston of the engine. This pressure is made to bear upon a steel spring, connected by a link at each end with a similar spring, supported at its centre upon a projection from the frame of the instrument. The pressure of the piston-rod upon the lower spring, causes the two springs to separate from each other, and the separation produced is, by a well-known law of deflection, directly proportional to the pressure sustained, so long as the deflections are small. A peculiar form, first suggested, (it is believed) by M. Morin, is given to these springs; one surface of the spring is plane, and the opposite surface is of a parabolic form, by which equal strength is given throughout every portion of its length. In a spring, thus formed, the deflection is distributed more equally throughout, and being thus diminished for a given separation of the springs at every point, the elastic limits are nowhere so soon exceeded.

By this connexion of the piston-rod with the springs, its position is made to vary directly, as the effective pressure upon four square inches of the area of the piston of the steam-engine, so that every additional pound in that pressure, will cause the piston-rod to alter its position, by the same additional distance in the direction of its length.

VOL. XXI.

2 c

A steel wheel, (termed the integrating wheel,) having the edge milled, turns upon the piston-rod as its axis, traversing with it also in the direction of its length. Through the arms of this wheel pass three rods, connected at their extremities by two pieces, so as to form with them a rigid frame, which turns, in fixed bearings, upon hollow axes, through which the piston-rod passes, so that the integrating wheel is free to traverse longitudinally upon the frame, but cannot revolve without carrying the frame with it. The integrating wheel is made to revolve by the rotation of a cone, which is held in contact with it by a spiral spring, acting constantly against the extremity of the axis of the cone. A system of bevil-wheels communicates to this cone the rotation of a pulley, which is driven by a cord carrying a weight at one extremity, and communicating by the other with the piston-rod of the engine, or with some point whose motion accords with it, but travelling through a less space. The circumference of the pulley moving precisely as the piston, the angle described by the cone, in any period of time, must be exactly in proportion to the space described by the piston in that time. The circumference of the integrating wheel, moving with that part of the cone with which it is in contact, the portion of a revolution, which it is made to describe in a given time, is dependent, first, upon the angle which the cone describes about its axis, during that time; and secondly, upon the distance of its point of contact from the apex of the cone at that time. If either of these two elements of variation remained always the same, then the portion of a revolution, made by the wheel, would vary directly as the other; whence it follows, by a well-known principle of variation, that when both these elements vary, it varies as their product; or that the portion of a revolution, made by the integrating wheel in a given time, varies directly as the product of two factors, one of which is the angle described during that time by the cone, and the other the distance of the point of contact of the wheel and cone, from the apex of the cone. The former of these factors varies directly space described by the piston of the engine, and the latter as the effective pressure then exerted by the steam upon the pis

as the

ton: therefore the portion of a revolution made by the integrating wheel, varies as the product of the space described by the piston of the engine during a given time, by the effective pressure of the steam upon it during that time; that is, it varies as the work or dynamic effect of the steam upon the piston during that time; whence it follows, that the number of revolutions or parts of a revolution made by the integrating wheel, during the stroke, is proportional to the whole work, or dynamical effect of the steam upon the piston during the stroke.

By a train of toothed wheels, the number of revolutions of the integrating wheel is registered to five places of integers, and to one place of decimals. The number registered is not diminished by the backward motion of the cone during each return stroke, because the integrating wheel ascends to the apex of the cone, and remains there during each return stroke, so that no number is registered during that interval.

In order effectually to guard, however, against any error which might arise from this reversed motion of the piston, a combination of wheels has been introduced, by which the revolution of the cone can be arrested during the return stroke; and to adapt the instrument to register (if required) every stroke, a fourway cock has been constructed, by which one of the Indicator cylinders may be made to communicate always with the steam end of the steam-engine cylinder, and the other to be acted upon by the vacuum end: in this case the movement of the cone should be constantly forwards.

The Professor then gave the mathematical formula, by which the work is determined from the numbers registered by the IndiHe then described the difference between the instrument and that of M. Morin, for applying the principle of M. Poncelet, to consist:

cator.

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First. In all those mechanical combinations which are peculiar to the instrument in its application to the steam-engine.-M. Morin's instrument having been applied to measure the traction of horses.

Secondly. In the surface of a cone being substituted for the

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