however, certain advantages peculiar to the turbine which do not belong to the water-wheel; namely, that it can be made. to work waterfalls of from 300 to 400 feet in height; and what is of considerable importance as regards efficiency is, that it works well in back-water.

There are three different descriptions of turbines.

1st. Turbines in which the water passes vertically through the wheel.

Wheels of this class are composed of two annular cylinders, the upper fixed and the lower revolving on a vertical axis. The upper is fitted with guides to direct the water most efficiently against similarly curved vanes or buckets, turned in the opposite direction, in the lower wheel. The water passes from the reservoir or cistern, placed over the upper cylinder, vertically downwards, acting on the revolving wheel by pressure as it glides over the surface of the vanes. Burdin, about 1826, invented a turbine of this description (turbine à évacuation alternative), the efficiency of which was about 67 per cent. of the theoretical fall.

2nd. Turbines in which the water flows horizontally and outwards.

In turbines of this class the revolving wheel is placed outside of the fixed wheel, so that the water directed by guide-plates on the inner wheel strikes the curved vanes of the outer wheel, and forces them round by pressure and reaction. The water is regulated by a cylindrical sluice fitting between the fixed and movable wheels.

*

M. Fourneyron's turbine is the chief example of this class. Its advantages, as stated by M. Poncelet in his report to the Academy of Sciences at Paris, are the high velocity at which it may be worked without reducing its useful effect, its small size, and lastly, its capability of working equally well under back-water. From the experiments of M. Morin, the coefficient of useful effect appears to range from 0·60 to 0.80. On the other hand, it has to the full the defects of this class of machines, requiring the utmost nicety of design and execution, and being very susceptible of injury from small bodies carried into it by the water. It requires for its successful application both a large acquaintance with the principles of its construction and a considerable experience of its use.

3rd. Turbines in which the water flows horizontally inwards; vortex wheels.

We owe the invention of this class of turbines to Professor James Thompson, C.E., of Belfast, and probably no turbines

* The coefficient of useful effect is the per-centage of the power expended as compared with the work accomplished,

are more efficient or capable of more general application to every variety of fall than the vortex wheels which he has constructed.

The peculiarity of these vortex wheels consists in the arrangement of the fixed guide-blades on the outside of a circular chamber, in which is placed the revolving wheel, so that the water flowing inwards strikes the curved plates of the revolving wheel tangentially, and leaves the wheel at the centre at a minimum velocity; the whirlpool created in the wheel-chamber giving to this description of turbine its designation of vortex wheel. These wheels are constructed by Messrs. Williamson & Brothers, of Kendal, who, we believe, have at present erected all that are employed in this country.

In addition to the horizontal wheel or turbine, there are centrifugal pumps and water-pressure engines. The first and most important is by Mr. Appold, and to that gentleman the country is indebted for many ingenious mechanical contrivances. Messrs. Gwyne have also contributed to the centrifugal pumping system, and both have splendid specimens of their different constructions at the Exhibition. The principle on which this machine is based, is a small wheel, which is driven at a great velocity, as many as from 800 to 1,000 revolutions per minute, at the bottom of the suction-pipe. This wheel or fanner with blades is driven by a steam-engine, and, revolving at great speed in a tight box, forms a vacuum in the suction-pipe and forces the water before it, up the discharge-pipes to the required elevation.

These machines are simple and effective where the water has not to be raised to a great height, but they are inapplicable for high lifts, and require a considerable amount of power to overcome the friction and pressure of water in the pipes. It is a question yet to be solved as to whether they are equal, on the score of economy, to the common pump. In fact, they are the same as a scoop wheel surrounded by water in a close box.

Those who have witnessed the imposing effect of these machines at work in the Exhibition, cannot be otherwise than struck with the large body of water which they discharge at a height of 12 to 15 feet, and without entering into comparison as to cost or the force employed to raise a given quantity of water, we nevertheless arrive at the conclusion that this system of raising water is well entitled to consideration.

The water-pressure engine, exhibited only in models and drawings, is employed for the same purpose as the centrifugal pump. Steam-power is not used in this case, but is obtained from the pressure of a column of water, which, acting upon a plunger, generates a reciprocating instead of a rotatory motion,

Engines of this description have been long employed in the mining districts of this country and the Continent. Professor Rankine states, that for the most successful application of these engines, as regards efficiency, it is necessary that the motion of the water should be slow, and as far as possible without shock. Three to six strokes per minute, or a velocity for the piston of one foot per second, is about the ordinary speed. The stroke also should be long, and therefore "the most advantageous use to which a water-pressure engine can be put is the pumping of water, to which slow motion and a long stroke are well adapted, because they are favourable to efficiency, not only in the engine, but in the pump which it works."

Grinding, Crushing, and Cutting Machines.-The Exhibition has been fruitful in this department of machinery, some of them being exceedingly well constructed, and entitled to every commendation for the high finish bestowed upon them. Of late years corn-mills have been greatly improved, and the system of arranging the millstones in a line along one side of the mill, and rendering the whole of the processes self-acting by an improved system of cleaning, brushing, and separating the grain with elevators, Archimedian screw creepers, and an improved process of wire and silk dressing, give a degree of perfection to the manufacture that could not be attained when the grinding machinery was less perfect. Several small mills, chiefly on the French system of driving the stones with belts, are exhibited; and others with high-pressure horizontal engines, driving from two to four pairs of stones, are entitled to notice for convenient arrangement and the superior finish of the workmanship.

Several examples of machinery for the colonies are exhibited from Liverpool and Glasgow, and most of these are of a class calculated to meet all the requirements of complete trains of sugar-machinery; as comprised in the steam-engine, rolls for crushing the sugar-canes, evaporating-pans, and centrifugal machines. In this description of machinery there is no particular novelty or improvement, excepting only the steamengine, which of late has undergone some change in rendering the whole apparatus more portable and convenient for exportatation. In oil and powder mills the examples were not striking at the Exhibition, if we except the grinding and compressing apparatus of Messrs. Samuelson & Co., of Hull. That firm exhibited a complete set of hydraulic pumps and pipes, for extracting the oil from the seed inclosed in canvas bags. They also exhibited a pair of edge-stones in motion, which created considerable interest as a point of attraction to visitors during the exhibition.

The Machinery for the Manufacture of Textile Fabrics comprises the largest class of ingenious machinery and clever contrivances ever submitted to public inspection; and these may be divided into machinery for the manufacture of cotton, for flax, and for wool, including stranding and rope machinery of every description. The length of this article, and our limited space, will prevent us from noticing in detail the numerous machines now in use in the different processes of manufacture, from the raw material to the finished article ready for the market. In cotton alone we have no less than from twelve to fifteen preparatory machines, in as many distinct processes, before the article is converted from the cotton into cloth; and these are distinguished as machines for opening, blowing, carding, drawing, slubbing, roving, spinning, winding, wooping, dressing, and weaving, exclusive of other subordinate processes. In all these operations may be seen an automaton system of movements, regulated with the same precision and nicety as a timepiece. It appears almost fabulous, the amount of work done and of power expended in this department of manufacture alone, and the number of hands employed, not as prime movers, but as "tenters" feeding the machines, unhappily no longer in daily use, for the production of this colossal manufacture. Many of our readers may not be acquainted with the magnitude of this important branch of national industry; but we may venture roughly to state, that the annual value of this manufacture is upwards of £70,000,000 per annum, and gives employment to nearly one million of persons, or, with its dependencies, upwards of two millions.

The cotton machinery is well represented in this year's Exhibition, by Messrs. Platt, Hetherington, Dobson, and others; and the adaptation, style, and character of the machinery are of the first order, and do the mechanical genius of this country great credit. All the minutiae of construction. appear to be attended to, and the utmost care observed, so that all the preparatory processes are performed by the machines, with a degree of exactitude far exceeding that of the human hand. Of late years a most ingenious machine has been introduced from Alsace, in France, as a substitute for carding. It is a combing machine, and its operations are so exact, and its work so perfect, as to enable the spinner to produce a finer description of yarn from an inferior quality of cotton. This machine is available for the finer numbers of yarn, and is one of the most important inventions since the days of Arkwright and Crompton. It has undergone great improvements since its introduction into this country, and is now extensively employed in the preparatory processes for flax and wool, as well

as cotton.

The power-loom combines within itself many important improvements in twills and figure-weaving. The revolving shuttlebox, and the changes that may be effected in colour and form, cause a close run between it and the Jacquard; and many of the beautiful fabrics in cotton, wool, alpacas, and mixed goods, are woven by these looms, and that with a degree of despatch equivalent to nearly forty yards of cloth per loom per diem. To this department of machinery the contributions have been large and successful, and pattern looms from almost every district distinguished for a particular manufacture have been exhibited.

The same degree of progress is observable in flax machinery as in cotton; and the screw-gill machinery first introduced by the late Sir Peter Fairbairn is strikingly exemplified in the Exhibition. A whole train of this machinery, consisting of heckling, carding, roving, and spinning, is exhibited by different makers; and judging from the superior workmanship and adaptation of the machines to the various processes, we should infer, that in flax the same progressive improvement exists as in that of cotton or any other description of manufacture. The same may be said of the long wool, alpaca, and mohair manufacture; but it is much to be regretted that samples from the great works of Saltaire have not been exhibited. The Exhibition has not been well represented in short-wool machinery; but several specimens from Leeds and the West of England are to be seen, exhibiting improvements on the old system of manufacture. From Belgium there are, however, some very good machines, together with several ingenious contrivances for the preparatory process, and for the ultimate finish given to the cloth. In the manufacture of woollen cloth, the Belgians are not behind, if they are not in advance of the manufacturers of this country.

Locomotive Machinery and Railway Plant.-Of all the changes effected by steam, that of locomotive travelling on a road of iron is the most wonderful, and this country has reason to be proud that it has cradled and nursed this Herculean machine from infancy to maturity. It is not the invention of one individual, but the labour of many; and none have done more for insuring its efficiency than the two Stephensons, father and son; not that the late George Stephenson had any extraordinary inventive powers, but he possessed a keen sense of observation, and an indomitable perseverance in every pursuit in which he was engaged; and hence followed his great success as a railway engineer. It is curious to trace the early beginnings and history of this machine from the time of Trevethick and Blenkinsop (as given by Mr. Smiles in his interesting work, "The Lives of the Engineers"), to its final completion in its