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Mechanical and Useful Arts.


(See Frontispiece.)

THE present state of the Tunnel will be best illustrated by the plan facing the title-page. From the annual meeting in March, 1839, to that in March, 1840, the rate of the progress of the works has steadily increased, with which there has also been a decreasing average cost per foot. In 1836, there were 117 feet completed; in 1837, only 28 feet; in 1838, 80 feet; in 1839, 194 feet; and from January 1 to March 1, 1840, have been completed 76 feet, being at the rate of 460 feet per annum; and the Tunnel is now completed to within 60 feet of the Wapping shore. Meanwhile, the public curiosity to inspect the Tunnel has increased with the progress of the works: in 1838, it was visited by 23,000 persons, and in 1839, by 34,000 persons; being an increase of 35 per cent. The works have now been in progress 15 years; the total sum expended, including the money advanced by Government, 363,000l.; and the Tunnel will be altogether completed for less than 500,000l. It is calculated that one archway will be opened throughout for foot passengers, towards the close of the present year.*


M. ARAGO, in his Memoir of James Watt, notes: "At a time when so many people are occupied with projects of rotatory steamengines, it would be unpardonable were I not to state that Watt had not only thought of them, (of which we find proof in his patents,) but had actually constructed them. Mr. Watt subsequently abandoned them, not because they did not work, but because they appeared to him decidedly inferior in an economical point of view to machines of double power and rectilinear oscillations.

"There are, in fact, few inventions, great or small, among those so admirably combined in our present steam-engines, which are not the development of some of the original ideas of Watt. Examine his

* Abridged from the Report of the Annual Meeting, March 3, 1840.

labours, and, in addition to the principal points minutely enumerated in the text (of the memoir,) you will find that he proposed machines without condensation, in which, after having acted, the steam is dispersed in the air; and which were intended for localities where large quantities of water could not readily be procured. The operation of the principle of expansion in machines with several cylinders was also one of the projects of the Soho engineer. He suggested the idea of pistons, which should be perfectly steam-tight, although composed exclusively of metal. It was Watt who first had recourse to mercurial manometers for measuring the elasticity of steam in the boiler and the condenser; who conceived the idea of a simple and permanent gauge, by whose assistance might always be ascertained, with a glance of the eye, the level of the water in the boiler; and who, to prevent this level ever varying injuriously, connected the movements of the feeding-pump with those of a float; and who, when required, placed in an opening in the cover of the principal cylinder of the machine, the indicator, a small apparatus so constructed that it accurately exhibits the state of the steam, in relation to the position of the piston, &c. Did time permit, I could show that Watt was not less skilful and happy in his attempts to improve the boilers, to diminish the loss of heat, and to consume those torrents of black smoke which issue from common chimneys, however elevated they may be.

"The younger Mr. Boulton informs us, that in the year 1819, the establishment at Soho alone had manufactured of Watt's machines, a number, whose steady labour would have required not fewer than 100,000 horses; and that the saving result from the substitution of these machines for animal labour, amounted annually to more than 3,000,000l. sterling. Throughout England and Scotland, at the same date, the number of these machines exceeded 10,000. They effected the work of 500,000 horses, or of three or four millions of men, with an annual saving of from 12,000,000l. to 16,000,000%, sterling. These results must, by this time, be more than doubled."-Translated in Jameson's Journal.


ON March 13, Mr. J. S. Russell submitted to the Society of Arts for Scotland, a very beautiful and scientific application of a mathematical proposition to the mechanism of the steam-engine. By this method, the piston-rod is carried up and down in a straight line, which is mathematically correct; while, by the method of Watt, the piston-rod is never at any one point carried in an absolutely straight line, and at top and bottom of the stroke it is very considerably deflected from the straight line, which gives rise to much friction and strain on the mechanism.-Jameson's Journal.


A LAW has been promulgated in Belgium, dated June 24, 1839, which, among other enactments, determines the thickness of iron or copper which shall be used for various sizes of boilers, to be worked at certain pressures. The particular description of safety valve to be used

is also described and figured. Every boiler must have two valves, one of which is to be kept locked, and inaccessible to any one except the head of the establishment to which the engine belongs. The weights upon the valve are to be examined and placed by a public officer entrusted with the matter, and are not to be increased without his intervention, on any pretence whatever. The boilers of stationary engines are to be supplied with a pressure gauge of mercury acting in the open air. Boilers of locomotive or marine engines are to have pressure gauges acting by compressed air, graduated so as to express the strength of the steam in the boiler. These gauges are to be so placed that the engineer or fireman attending the working of the boiler, shall be able to observe the pressure of the steam with facility.-Mechanics' Magazine; abd.


MR. RUTHVEN, of Edinburgh, has patented a Steam-boiler, which practises slower combustion than usual, and thus insures less destruction of the boiler, and economy of fuel; the patentee being of opinion that "when the boiler is highly heated, the water is actually repelled from the surface of the plates by an atmosphere of caloric, from its not being able to absorb it with sufficient rapidity."

Mr. Ruthven has adopted a round boiler, about 2 feet diameter, and any required length; which form gives a strength that will sustain, with three-eighth plates, upwards of 800 lb. pressure per square inch; but the great desideratum, surface, was wanting; which has been gained by forming into a spiral form 500 to 1,000 feet, or more, (according to the size of engine,) of malleable iron pipe, of an inch diameter, more or less, as required: this spiral represents a stillworm of from 12 to 15 inches diameter; it is placed in the flue leading from the fire, and through which the heated air must pass in its way to the chimney; one end of the spiral is connected with the boiler under which the fire is placed, the other end being attached to the pump for supplying the water. Thus is exposed the whole surface of the spiral in the flue to the action of the heat passing through and around it; while the water is extracting the caloric in its passage to the boiler, the heated air passes into the chimney where the coldest of the water enters the spiral, and before the water enters the boiler, it is ready for converting instantly into steam. Besides the objects stated, this arrangement is stated to give strength, durability, and economy, with more security from steam power than has yet been obtained.


MR. F. WHISHAW, C.E., having been requested to examine and report on the principle of construction of this engine, (also known as the Stoke Prior Engine,) has inspected six different ones, and reports them to have performed their duties satisfactorily. One of these engines, (Mr. Whishaw observes,) has been working for fifteen months, and has only required during this period, the expenditure of 3s. for repairs. In his examination, Mr. Whishaw has paid especial attention to two important points. First, he finds the moving parts of this engine to be so few in number, and their motion so uniform and regular, that the

amount of friction must be very materially reduced; wherefore the wear of these moving parts, and their liability to derangement will be proportionally reduced. Secondly, with regard to the quantity of steam required to perform a certain amount of work, Mr. Whishaw reports that, from several trials made with an engine of this construction at the works of the British Alkali Company, near Bromsgrove, he found the work done by a 24 inch Disc Engine, working with the steam at 29 lb. pressure, to equal 20-horse power, with due allowance for friction; and the consumption of coal, (common Staffordshire), in general to 2 cwt. per hour, or rather more than 11 lb. per horse, per hour. This engine is worked by high 'pressure steam, which, after performing its duty, passes into the atmosphere: during the experiments, the average pressure was found by the mercurial steam gauge, to be equal to 29 lb. on the inch; but, in order to work the machine to the greatest advantage the pressure should be considerably increased. This engine equal to 20-horse power, with steam at 29 lb., would, with steam at 431⁄2 lb., be equal to 30-horse work. It occupies a space equal to 4 feet square by 7 feet high, and its whole weight, including the frame, is 1 cwt. 43 qrs. 16 lbs.; but a requisite increase of the weight of the frame would probably increase the whole to 2 tons; whilst the weight of a high pressure reciprocating engine of equal power would be not less than 20 tons. -Midland Counties Herald; abridged.


MR. ROWLEY, of Manchester, has invented a Rotary Engine, combining simplicity of construction with rapidity of motion, greater power than a common engine of the same size, and a saving in fuel of upwards of 20 per cent. This engine consists of a circular steam-tight case, in which revolves a wheel of such a diameter as to leave a sufficient space round its circumference, for the action of the steam; this space being divided into two equal parts by a solid abutment, on the sides of which the induction and eduction of pipes are placed. This wheel is fitted with two or three pistons, which work within the wheel, so as to pass the abutment, afterwards projecting into the steam chamber, and forming a resisting surface against which the steam acts, and consequently propels the wheel, the axis of which passes through the case, and is connected with the shafting of the machinery to be put in motion. The action of this machine is extremely beautiful; no levers, beams, pistons, or crank plunging about, but all smooth, circular, rapid, and noiseless.-Manchester Chronicle.


ON May 25, an engine manufactured in Cornwall by Messrs. Harvey and Co., of Hayle, from the specifications and plans of Mr. W. West, for the Carlisle Canal Company, commenced working, for the supply of the canal from the river Eden. The water has to be lifted 56 feet; the steam cylinder is 60 inches in diameter; that of the pump, 45; length of the stroke, 10 feet. In less than three minutes, the water was lifted to the pump-head, whence it was poured forth in a continuous and rapid stream, at the rate of 6,624 gallons per minute: consequently, working

at twelve strokes, the quantity delivered in twelve hours into the canal is 4,769,280 imperial gallons of water, equal to 763,200 cubic feet, at an expense of fuel under 5s.

Mr. West's engines, at the Fowey Consols Mine, in Cornwall, on a trial, lifted 125 million pounds weight one foot high with 94 lbs. of coal, and averaged upwards of 90 millions during 12 consecutive months. At the Portsmouth and Farlington water-works, the consumption has been reduced, (doing more work,) full 75 per cent. W. Wicksteed, the engineer of the East London water-works, computes their saving at 70 per cent., viz., 1,2977. 16s., instead of 4,3281. 2s.-Carlisle Journal.


MR. RODDA has patented a means of Consuming Smoke, by means of parting off a portion of the back of a furnace with fire-brick, so that when the coal has been coked in the forepart, it is thrust into the hinder division; and the smoke from the freshly-supplied coal being made to pass over the incandescent coked fuel, is consumed. The principal merit of this invention is its simplicity; consisting merely of a few fire-bricks, which may be placed in any furnace without expensive alteration.- Mechanics' Magazine.



A STEAM-BOILER, of 20-horse power, built by Mr. Borrie, of the Tay foundry, has been so constructed as to consume its own smoke. The contrivance is as simple as it is efficient. There are no steamjets, pipes for communicating heated air, blowing machines, or complicated apparatus, of any description, connected with it. No aid from a philosophical stoker is required, nor any attention is necessary more than is bestowed in the firing of common furnaces. A considerable saving of fuel is also effected, which, however, does not wholly arise from the consumption of the smoke, but is effected partly from the otherwise improved construction of the boiler. The additional expense of the boiler over those of the common construction is so small as scarcely to enter into the computation. The furnace is surrounded by water spaces (thus wholly within the boiler), and has two series of fire-bars. The first series, or those next the furnace door, is fixed at a considerable inclination. The second series is placed farther in, and below the first series, and has no inclination. The anterior extremities of the former project a few inches underneath the posterior extremities of the latter. Immediately above the posterior extremities of the first series of fire-bars, is a water partition guard, attached to the upper part of the furnace. Between the furnace door and this guard, a chamber is formed, which may be denominated the coal-chamber, that being the place into which the coals are put for feeding the furnace. Sufficient vertical space, between the first series of bars and the water partition guard, is left to admit of the coals falling down into the posterior or smoke-consuming chamber, after having been coked in the first or coal-chamber. The relative position

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