The city of Philadelphia was for many years supplied with water by means of a low-pressure engine; Mr. Evans, the Trevithick of America, has, however, lately substituted a high-pressure engine in its place. By this means, in fuel alone, a saving of seventeen dollars per day has been effected.

Trinidad appears to have been the first West Indian colony in which the resident planters could overcome their ancient prejudice in favour of the cattle mills, which are still generally employed on sugar estates. Mr. William Lushington, who had a considerable property on that island, introduced a large engine by Boulton and Watt in 1804; and so great was the saving effected by its use, that the labour of three mills, each of which were equally expensive, was usually performed by the one machine.

From the result of some experiments lately made with two steam engines, constructed by Mr. Maudslay for the island of Ceylon, it appears, that this species of power has been equally efficient in the dressing of rice and preparation of oil. The apparatus employed for this purpose was contrived by Mr. Hoblyn, a gentleman well known for his distinguished scientific attainments, and it has been found that, allowing three hundred working days in the year, and the engines to work ten hours per day, they would annually convert 576,000 of paddy into a quantity of rice equal to 147,347 bags, which, at nine rix-dollars a bag,

reader's attention. In his engine, Mr. Masterman proposes to employ water as the propelling power, which he effects, by enclosing it in the tubular rim of a large wheel, furnished with valves opening in one direction. This wheel is made to revolve on a hollow axis connected with the steam boiler. The arms which radiate from the axis are also hollow; and on the admission of steam from the boiler, it is conducted through the arm immediately opposite, and entering the rim of the wheel, comes in contact with, and presses against the column of water on the one side, and the closed valve on the other. The water being previously heated to the boiling point, no condensation ensues, but the whole weight of water, which was previously balanced in two columns of equal length, is driven by the pressure of the steam to the side opposite to that at which the elastic vapour entered, and that side of the wheel will necessarily preponderate. If this process be repeated, the steam being allowed to blow through each radiating arm in succession, a continuous rotatory motion will be produced. Should it be found adviseable to employ steam of less elasticity, a condenser may be added, and this too without materially increasing the expense.

In Messrs. Boulton and Watt's Bell-crank Engine, the cylinder is supported by brackets proceeding from a cast-iron condensing-cistern, and is placed over one end of it. The beam which is formed like a right-angled triangle, has its centre of mo

the impossibility of draining them by manual labour, applied to Mr. Trevithick of Camborne in Cornwall, one of the patentees of the high-pressure engine. This ingenious mechanic applied himself with such extraordinary diligence to the subject, that in less than nine months the materials for as many engines were completely ready for their destination. This apparatus, which cost about ten thousand pounds, left Portsmouth in the beginning of September, 1814, accompanied by M. Uville and three Englishmen, to direct the erection of the machinery.

Mr. Trevithick was afterwards employed to superintend the Royal Mint established at Lima, and on his arrival in South America, was received with such enthusiastic gratitude, that the Lord Warden proposed to erect his statue in massive silver. The engines employed were exclusively on the high-pressure principle, and will be found under his patent in the Appendix to the present work. Indeed this appears to be the only engine likely to act with an advantageous effect, the extreme rarity of the atmosphere in those elevated regions, precluding the economical use of the common engine.

We have hitherto viewed the steam engine, when employed as a substitute for animal force, in giving motion to mills, raising of water, and a variety of other employments, all of which, however, are of a fixed and stationary nature. But some progress has likewise been made towards the applica

E

tion of the same power to moveable machinery, and when constructed for this purpose it is called a locomotive engine.

The employment of an internal mechanism to impel waggons on a plane road is of very early date, but the first application of the steam engine to this purpose took place, we believe, in the Royal Arsenal at Paris, towards the close of the last century. From this time till 1802, but little progress appears to have been made in the use of this species of wheel carriage; but about the latter period, Mr. Trevithick commenced a series of experiments on the use of the high-pressure engine for the above purpose; and this, with some improvements, has since been adopted.

When these engines were first tried, it was found difficult to produce a sufficient degree of re-action between the wheels and the track road, so that the former turned round without advancing the vehicle. This was remedied by Mr. Blenkinsop, who, when he adopted this species of conveyance, took up the common rails on one side of the whole length of the road, and replaced them with rails which had large and coarse cogs projecting from the outside. The impelling wheel of the engine was made to act in these teeth, so that it continued to work in a rack the whole length of the road.

An engine of four horses' power, employed by Mr. Blenkinsop, impelled a carriage lightly loaded at the rate of ten miles an hour, and when con

nected with thirty coal waggons, each weighing more than three tons, it went at about one-third

The application of the steam engine to impel carriages on the public roads, has hitherto been considered as a refinement in mechanics, rather to be wished for, than a matter of reasonable expectation. It has however been stated, that a vehicle of this description is now constructing in Ireland, intended as a stage-coach, and it is added, that when loaded with a weight equal to four tons, it will be enabled to advance at the rate of fifteen English miles per hour. But it must, we think, be sufficiently apparent that the employment of this species of prime mover on a common gravel road, would be in the highest degree destructive, and a considerable increase in the toll would be the certain consequence.

In proof, however, that the necessity of employing an iron track-road for these vehicles is not so serious an objection as at first view might be supposed, more particularly in our mining districts, the neighbourhood of Newcastle alone, affords, within an extent of twenty-eight square miles, more than seventy-five miles fitted for this species of conveyance; and it is a well known fact, that there are many situations in which iron rail-roads might be advantageously employed, in which it would be quite impossible to open a navigable canal.