common wheels is so great, as materially to affect the ease and safety of a vessel in a rough sea.

9thly. Vessels with revolving paddles are enabled to employ to advantage engines of a much greater power, and with commensurate speed, than if fitted with common wheels. Vessels with common fixed paddle wheels, like the post-office packet at Holyhead, when running before the wind in a gale and a heavy sea, cannot employ the full power of their engines with safety, the wheels then running two or three times round without touching the water between the trough of the sea, and then being brought up all at once, are in great danger of causing some part to give way.

. The use of these revolving paddles has been already adopted in the Waterloo steam vessel, plying between Dublin and Liverpool; and in the Havre de Grace, iron steam vessel, now on the Thames.

We have thus given the outlines of this truly important and valuable paper. In some of our future numbers we shall most probably give some of the more mechanical details.

The Tread-Mill.

ALTHOUGH we are not in the number of those who think that labour itself, and more especially what has been termed hard labour, can or will effectually and completely reform the evil dispositions of the criminal (believing, as we do, that a higher and more intellectual power must be in operation before all which we desire in the reformation of the criminal will be effected), yet as the Tread-Mill offers more humane means than have been hitherto practised in our criminal jurisprudence and management, we give place to a description of it, trusting, at the same time, that this evident amendment in prison

discipline is a step to still greater and more benevolent reforms.

The wood-cut exhibits a party of prisoners in the act of working one of the tread-wheels of the discipline mill invented by Mr. Cubitt, of Ipswich, and recently erected at the House of Correction for the county of Surrey, at Brixton. The view is taken from a corner of one of the ten airing yards of the prison, all of which radiate from the governor's house in the centre; so that from the window of his room he commands a complete view into all the yards. A building behind the treadwheel is the mill-house, containing the necessary machinery for grinding corn and dressing the flour; also rooms for storing it, &c. On the right side of this building a pipe passes up to the roof, on which is a large cast-iron reservoir, capable of holding some thousand gallons of water, for the use of the prison. This reservoir is filled by means of forcing pump machinery below, connected with the principal axis which works the machinery of the mill. This axis, or shaft, passes under the pavement of the several yards, and working by means of universal joints, at every turn, communicates with the tread-wheel of each class.

This wheel, represented in the cut, is exactly similar to a common water-wheel; the tread-boards upon its circumference are, however, of considerable length; so as to allow sufficient standing room for a row of from ten to twenty persons upon the wheel. Their weight, the first moving power of the machine, produces the greatest effect when applied upon the circumference of the wheel at or near the level of its axle. To secure, therefore, this mechanical advantage, a screen of boards is fixed up, in an inclined position, above the wheel, in order to prevent the prisoners from climbing or stepping up higher than the level required. A hand-rail is seen fixed upon this screen, by holding which they retain

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their upright position upon the revolving wheel; the nearest side of which is exposed to view in the plate, in order more distinctly to represent it, than could otherwise have been done. In the original, however, both sides. are closely boarded up, so that the prisoners have no access to the interior of the wheel, and all risk of injury is prevented.

By means of steps the gangs of prisoners ascend at one end, and when the requisite number range themselves upon the wheel, it commences its revolution. The effect then to every individual is simply that of ascending an endless flight of steps, their combined weight acting upon every successive stepping board, precisely as a stream of water upon the float-boards of a water-wheel.

During this operation, each prisoner gradually advances from the end at which he mounted towards the opposite end of the wheel, whence the last man, taking his turn, descends for rest; another prisoner immediately mounting, as before, to fill up the number required, without stopping the machine. The interval of rest may then be portioned to each man by regulating the number of those required to work the wheel with the whole number of the gang. Thus, if twenty out of twenty-four are obliged to be upon the wheel, it will give to each man intervals of rest amounting to twelve minutes in every hour of labour. Again, by varying the number of men upon the wheel, or the work inside the mill, so as to increase or diminish its velocity, the degree of hard labour or exercise to the prisoner may also be regulated. At Brixton, the diameter of the wheel being five feet, and revolving twice in a minute, the space stepped over by each man is 2193 feet, or 731 yards, per hour.

The wheels erected at the House of Correction at Coldbath-fields are each capable of containing forty or

more prisoners, and the joint force of the prisoners is expended in giving motion to a regulating fly, which, by expanding of itself in proportion to the power, will keep any number of men, from twenty to three hundred and twenty, at the same degree of hard labour.

To provide regular and suitable employment for prisoners sentenced to hard labour has been attended with considerable difficulty, which the invention of the discipline mill will completely obviate; and it is presumed that, when its advantages and effects are better known, it will be universally introduced into our Houses of Correction. This labour is remarkable for its simplicity. It requires no previous instruction; no taskmaster is necessary to watch over the work of the prisoners; neither are materials or instruments put into their hands that are liable to waste or misapplication, or subject to wear and tear: the internal machinery of the mill, being inaccessible to the prisoners, is placed under the management of skilful and proper persons, one or two at most being required to attend a process which keeps in steady and constant employment from ten to two hundred or more prisoners at one and the same time, which can be suspended and renewed as often as the regulations of the prison render it necessary, and which imposes equality of labour on every individual employed, no one upon the wheel being able, in the least degree, to avoid his proportion.

As the mechanism of the tread-mill is not of a complicated nature, the regular employment which it affords is not likely to be frequently suspended by the repairs in the machinery; and should the supply of corn, &c. at any time, fall off, it is not necessary that the labour of the prisoners should be suspended; nor can they be aware of the circumstance.

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