ment; and which, it is trusted, will be the means of elucidating the true law of such resistance.

CHAPTER VII.-Ropes being most generally employed in dragging carriages up ascents, or lowering them down from one level to another on Rail-roads, by the aid of fixed steam-engines, or by the force of gravity, the friction of these will form a subject of enquiry of considerable importance. This chapter contains, therefore, a series of Experiments, on the friction of ropes, on several engine and self-acting planes in actual use; from which is deduced, a theorem for ascertaining the friction of ropes employed in dragging carriages upon any Rail-road.

CHAPTER VIII.-Comprehends a set of experiments, observations, and deductions,

on the various species of motive-power used on Rail-roads, divided into four parts, viz.

SELF-ACTING PLANES,

FIXED STEAM-ENGINE PLANES,.

HORSES, and

LOCO-MOTIVE STEAM-ENGINES.

In Self-acting Planes the moving power being the force of gravity, the action of which is well-known, and that action being communicated to the carriages by the medium of ropes; a practical theorem is given, founded on the friction of ropes, as ascertained by Experiment.

The effective performance of fixed steam-engines is, also, illustrated by four examples of engines dragging carriages up ascents on Rail-roads, from whence will be derived a rule for practical appli

cation.

pressure

Some regard should, however, be observed with respect to the effective power of high-pressure engines, acting solely by the expansive force of steam. In the elucidation of the loco-motive engines, it will be found, that the effective energy upon the load, compared with the upon the piston, (the latter being calculated by the elasticity of the steam in the boiler) depends in a great measure upon the velocity of the piston, and its load; and also upon the size of the aperture, through which the steam issues from the boiler to the cylinder, compared with the elasticity of the steam in the boiler. In those engines the size of the aperture was that which is most generally used, and which is about one twenty-fifth of the area of the piston. I have, also, given the velocity of the piston, so that, in the

B

application of similar engines to practice, a comparison can be made.

To establish data for the performance of horses, I have given Tables of the work of horses upon three different lines of road, two of which may be considered as most favourable for the application of horses, where the whole of the goods are conveyed in one direction, and where the relative weights are similar to those given in the Table. The horses of Table I. were very heavy and powerful; and those of Table II. rather more so. The Horses of Table III. may be considered as moderately-sized horses.

The average performances of these horses fall below the expression of Mr. WATT, and reach beyond that of Mr. SMEATON; but,

as Mr. WATT's expression was assumed more as a conventional standard for a horse's power, than the true measure of the energy which he is capable of exerting upon the load, perhaps those in the Table, being the result of long-continued practice, will be a more correct expression of his energy.

In the case of loco-motive engines, a sufficient number of Experiments are given, I trust, to elucidate both the laws which regulate their action, and, also, the extent of their performance and utility in the conveyance of goods upon Railroads. The uncertainty which exists, in general, respecting them, renders this extremely necessary; and, if I have been too prolix in the elucidation of their several modes of action, it has arisen from