from ths to inch, at the top, except the upper plate, which is ths. She is clencherbuilt, and double-rivetted throughout. To. wards the extremities, and quite aloft, the thicknesses are reduced gradually to 7-16ths.

"The ribs are framed of angle-iron, 6 inches by 3, by 4-inch thick at the bottom of the vessel, and 7-16ths thick at the top. The mean distance of the ribs from centre to centre is 14 inches; and all these ribs will be doubled: the distance is then increased to 18 inches, and then gradually to 21 inches at the extremities.

"The boiler platform is of plate iron, supported upon ten iron kelsons, of which the centre ones are 3 feet 3 inches deep. These kelsons are formed, like the floorings, of iron plates placed on edge. The hull is divided into five distinct compartments by means of substantial water-tight iron bulkheads.

"The decks which are of wood, consist of the cargo deck, two cabin decks, and the upper deck.

"It would be an endless task, and, without the aid of drawings, a fruitless one, to attempt a description in detail of the construction of this magnificent vessel. I can, however, state that her lines are very beautiful, and adapted to attain the highest rate

of speed. The general character of the workmanship is very good, and does great credit to the builder. Her exquisite proportions prevent that appearance of heaviness which is generally observable in large ships; and, although she is probably the strongest vessel ever built, she has a remarkable air of grace and lightness."

How this prodigious floating mass is to be propelled-that is, how the power of the engines is to be made available to the propulsion of the vessel-is not stated. We gather only from the breadth assigned for "the beam," and the absence of all mention of paddle-boxes, that it is not to be by paddle-wheels.

We take our leave of Mr. Grantham with our hearty thanks for the service which he has rendered by his publication, not only to the whole ship-building craft, but to the nation at large. He is the first who has set the subject of it fully and fairly before the public; and we venture to predict will do more by his little work; to promote the universal adoption of iron in the building of ships, than will be effected even by the launching of the Bristol Leviathan.

shore, feels great pleasure, after a variety of trials and failures, in laying his plans before the public for their inspection; at the same time, the inventor begs to state, that he does not intend to secure to himself the benefit of his discovery by patent right, but is anxious to throw open his invention to all parties who may choose to adopt it, without any remuneration whatever. The prefixed sketches will at once give the public an opportunity of judging of the correctness of his plans. Those who have taken notice of a fish in a strong current, must have observed that a fish checks its speed by the expansion of its fins against the fluid. It is also well known by every person connected with shipping, that a small piece of wood of an angular form is used on board of a ship, for the purpose of giving the rate at which the ship is sailing, (see fig. 4;) this is called the ship's log. This angular piece of wood, and line attached, is thrown into the sea; the bottom part of the wood being made much heavier than the top causes the wood to sink perpendicularly in the water with a rope fastened at each corner, which causes the flat part of the log to face the ship; by this means the log, having a body of fluid against it, remains stationary when the ship is going at the rate of ten knots an hour. also well known, that unless the small wooden peg which is placed in the top corner of the log comes out by a sudden jerk of the line, this small piece of wood will require two or three men to pull it towards the ship. The figures 2 are upon the same principle of the log, only upon an enlarged scale, or I might say upon the principle of a boy's kite in the water reversed; instead of pulling against air, it is pulling against an immense weight of fluid; there is this difference, the boy's kite is made of paper, and the water kite is made of strong timber, with strong ropes attached to the sides of the vessel. The water kites should be made heavy at the bottom and light at the top, so as to keep perpendicular in the water; fig. 2 is supposed to be the tail of the kite, 10 feet long, with a buoy made of cork, so as to swim upon the surface of the water, and to cause the water kites to rise and fall with the motion of the waves.

It is

A small rope (fig. 3) is employed to haul the water kites towards the ship horizontally: the ropes from the sides of the ship to the

water kite should be from 100 to 150 yards long, so as to give as much play as possible; the size and strength of the water kites, also the ropes, must be regulated according to the size of the vessel. The opinion of the inventor is, that the speed of a steam-ship of 400-horsepower, with her engines at full work, would be immediately stopped upon the same principle; in fact it is impossible to calculate the immense weight of fluid the ship would have to pull against.

There is another important advantage to be derived from the use of these water kites when vessels are off the land in foggy or hazy weather; by using them the ship would remain stationary, although in deep water, till the weather became clear. A case in point: the Forfarshire steam vessel, trading between Hull and Dundee, ran on the rocks off the Fern Islands, and became a complete wreck, during a very foggy night: this accident, and many others, might have been prevented, had the vessel been provided with the water kites, and use been made of them when the fog first came on. How much safer would it be for captains of ships, in foggy weather, when off the land, to lose a few hours rather than run the risk of so many lives, as well as property!

Sheffield, May 20, 1842.

J. JONES.

THE SMOKE NUISANCE-address AT THE MANCHESTER VICTORIA GALLERY — BY C. W. WILLIAMS, ESQ.

(Continued from vol. xxxvi, page 494.)

Of the modes of estimating the quantity of heat generated, and which is among the most difficult objects in the course of prac tical experiments, I will explain some of those by which I have obtained my results: -These are, 1st. The use of copper bars, one end of which is inserted in the flues; the other projecting outside, on which a thermometer is fixed. The use of these is shown by an engraving in the Mechanics' Magazine, No. 971.

These bars necessarily give but relative temperatures; as the heat, influencing the thermometers, has to be transmitted through the bars. At the foot of the chimney it was found that when the bar thermometer indicated 300°, the heat within the flue was at least 750°. This fact was ascertained by means of fusible metals placed within the flue. 2nd. The use of this series of fusible

metals specially prepared by Dr. Kane, and by which a close approximation was had to the actual temperature in the interior of the flues. 3rd. The aid of a pyrometer, which, by a series of metallic expansion bars, indicates the absolute heat within the flues, and thus affording a working point for observation.

As far as belongs to the combustion of the gases in thus preventing the genera tion of smoke, the eye alone is a sufficient guide, as it is in testing the perfection of the process in the lamps before us; but as regards the quantity of heat generated, we must have recourse to other means. In

small boilers the power of absorbing the increased quantity of heat that is made, is the more difficult from the limited absorbing surfaces they present. Let me suppose a boiler of a given size, capable of evaporating 500lbs. of water into steam in one hour, by 100lbs. of coal ;-let me suppose, by the application of an improved process, that an additional 50 per cent. of heat is generated. If the boiler be adequate to taking up this additional heat, 750lbs. of water will be evaporated.

Let me, however, suppose, that from its limited extent of heating surface, or other cause, it was only able to take up one half such additional heat-say 25 per cent;-in that case the remaining 25 per cent would necessarily be lost by escaping through the chimney. I ask, should we then be justified in estimating the economy of the new process of the furnaces by such measure of increased evaporation? and would it be safe or correct to estimate it at a gain of but 25 per cent, without also estimating the other 25 per cent which was lost, and which, under a better arrangement, or a better boiler, might have also been turned to the account of evaporation ? On this subject the experimental tin boilers, now before you, offer a satisfactory illustration. The experiments by these, and their varying results, are described in the Mechanics' Magazine, No. 954. We see how the mere change of position of the three boilers varies the evaporative results. Here we see the amount of evaporation is no test, or even approximation, to the value of any system of improved combustion.

At the late meeting in this room, the chairman asked Mr. Houldsworth the question, as reported, "What is your practical conclusion as to the quantity of steam generated, with respect to the quantity of fuel used?" Had the question referred to the quantity of heat generated, it would admit of a direct answer. I have already shown, that, had the question referred to the boiler and furnace now in Fennel-street, I must have given two distinct answers, as referrible

one.

to two distinct periods. At one time it would have been five per cent, and at another 35 per cent; and this without any alteration in the amount of fuel used or time employed. The same question was put to Mr. Parkes, in reference to the marine boiler, on which he experimented: his answer is 47 per cent. and in a much smaller boiler, yet it is manifest that this 47 per cent is still much below the true estimate; for he shows that the escaping heat was double what it had been the preceding day, when the boiler was tested under the old mode of furnace. In this boiler, the increased weight of fuel used, and the consequent increase in the waste by the chimney, was the result of requiring an increased quantity of steam, and thus forcing the small boiler to do the work of a larger In such cases the ordinary resource is what is called forcing the fires. This, however, is a manifest misnomer. It is in truth forcing the boiler. By this system of forcing, which is nothing more than repeated stirring and poking, greater heat is produced in the immediate region of the furnace; and hence the received notion, that enlarging the furnace increases the evaporation. This may be advisable under the old system, which depends almost entirely on the heat generated under the boiler, but not as applied to the new, which distributes the heat uniformly along the flues. Tredgold observes :—“The surface of boiler to produce a given effect must be sufficient to receive the heat which will produce the supply of steam; and, as fire or bottom surface is the most effectual, that kind of surface should be of sufficient area to receive the whole while the flue surface, or the effect of the smoke.

effect of the fire; sides, may receive Hence we have an

easy mode of determining the proportions." Again he says-" The flame and smoke must be kept in contact with the vessel, as long as it is capable of affording heat." Thus we see Tredgold looks on smoke as inevitable. Had Watt or Tredgold seen a system by which the evolved gases from a furnace were wholly converted into flame and entirely consumed without smoke, as in the lamp, having the flues filled with transparent products from that combustion, would they have continued to speak of extracting all the heat from the smoke? or would Tredgold have committed the great error of saying, that the flame is limited to six feet from the bridge with coal, and three feet from coke? What would he have said, had he witnessed Mr. Parkes's late experi ments on a marine boiler, in which the flame reached to 40 feet, and in which the eye could not be deceived? What would he have said, if I showed him, as I daily see, a flame of 20 to 25 feet from a furnace sup

plied with coke alone, and never under ten feet in length?

:

"The distance," says Tredgold, "to which the flame and heated smoke of a fire will extend so as to be effectual, will depend on the draught of the chimney and the nature of the fuel from three to six feet will be about the range in a well-constructed fireplace, that is, about six feet with coal and a good draught, and about three feet with coke and slow draught. This, of course, will regulate the length of the boiler." Nothing can be more unsound, and contrary to fact, the moment an improved system of admitting air to the combustible gases from which flame is produced, is adopted.

How then are we to account for these erroneous assertions, but by assuming, 1st, That he had not witnessed the proper combustion of the gases, which alone produces flame, and that he had not adopted the means of looking into the flues? That this latter would, however, have been useless without the former, is clear, as Mr. Parkes observes that he could not see a ray of light in the flues under the old system of excluding the air. Mr. Armstrong, following Tredgold, says in his treatise "We have never seen the flame go beyond the bottom of the boiler." I will show him the flame all round the boiler, as well as along the bottom; and I will do more: I will show him a continuous flame of 10 to 12 feet long from the bridge, at the very moment, and under the exact state of things, when he alleges that there is no flame at all; and even asserts that the admission of cold air behind the bridge, instead of actually producing that flame, as it does in fact, would so chill down the bottom of the boiler, as to cause the plates to contract, and drag the rivets into holes. This is alleged by him to have occurred in Hamnett's boiler, which, however, he never saw in action, as there was no means for internal inspection. If it were so, how did it happen that the rivets and seams were also dragged all over the boiler, and even to the crown of the boiler? I am not surprised that such dicta should have been hazarded, so long as there was no means of effecting the full combustion of the several gases evolved from the coal in a furnace, and no means of internal inspection to enable us to see that such was really the fact : but I am surprised that any one, at the present day, with the power of correcting his own erroneous impressions, should persist in upholding the fallacy, and endeavouring to persuade men, against the evidence of their senses, that a flame never extends beyond the bottom of the boiler when they see it extending above twenty or thirty feet farther: or, that when the fuel on the fire is

clear and incandescent, there is then no gas passing off and no demand for air, while, under such circumstances, they see (as stated in Mr. Parkes's report) a minimum flame of ten to twelve feet arising from the carbonic oxide thus generated, and requiring its due supply of air, as the carburetted hydrogen had previously done.

The importance of enlarging the boiler and its heat-absorbing faculty, is fully exemplified in the Cornish boiler. In Cornwall, they use enormously large boilers, above four or five times larger than are used in this county.

By this means, and by a system of internal flues and enlarged surfaces, a slow and more economic rate of combustion of the fuel is effected in equal times; for, after all, on this question of time the whole depends. Economy is two-fold, as to the fuel used, and the time employed. If we adopt a slow rate of combustion, (as shown in the table exhibited) or have large boilers as the Cornish plan, each square foot of surface will produce less evaporative effect, in any given time, but the quantity will be made up by extended surface. If, however, we have a more active combustion, or a smaller boiler, with less surface, more heat will be generated, in equal times, but necessarily at a sacrifice of greater waste from the increased temperature of the escaping gaseous products by the chimney.

The more active the combustion, the greater will be the ratio of loss arising from the escaping and unemployed heat; first, because the absorbing surface of the boilers are unable to take up all such additional heat in equal times; and, secondly, because the current or draught of the gaseous matter, carrying such heat through the flues, is also increased. In other words, the conducting power of the metal plates and the recipient or absorbing power of the water are not commensurate with the heat-generative power of the furnace and fuel. If then, in any given boiler, we require the largest quantity of water to be converted into steam from a pound of coal, and, without reference to time, we must have recourse to either large boilers or slow combustion: not because slow combustion produces more heat from the pound of fuel, but because it harmonizes more with the nature of the absorbing faculty which the boiler plates possess. Now this question of time is overlooked in practice, though quite as essential in drawing an inference, as the question of fuel used. Tredgold says, "It was well remarked by Mr. Watt, that the sole object of the arrangement of his boilers was to economize the fuel as much as possible. It is not the shallowness or depth of the boiler that produces

this effect, but the making of the boilers of such a shape, that the air which passes through the fire should be robbed of almost all its heat before it can escape." I ask, then, why not ascertain how much of the heat is thus taken up, and how much of it escapes? for the question of economy hangs as much on the quantity that escapes, as on that which is employed,-influenced, first, by the limited absorbing power of the boilerplate surface; second, by the greater quantity of escaping products from the increased draught; and, third, by the increased temperature of such products. Thus, the quantity of fuel used will bear a relation to all these terms, and not to the quantity of steam generated. Nature requires increased surface or increased time. Two superficial feet of absorbing surface, acting for one hour, may be taken as equal to one foot of surface for two hours,-the temperature in the flues being the same. A more perfect combustion can only be profitably brought into action and rendered available by two means, namely, by extending such surfaces, or by increasing its heat-absorbing and transmitting quality.

I would, then, caution experimentalists, that, in calculating the general economy of any system of combustion in the furnace by the weight of water evaporated, without taking into account the quantity lost by the chimney, and considering that quantity as équivalent to an increased evaporative power, such a mode of calculation would be deceptive in every sense. For, suppose 1,000 units of heat to be generated per second of time from one pound of coal, the weight of water evaporated will depend on the number of those units absorbed by the water. If 800 be absorbed, 200 will be lost; if 500 only be absorbed, 500 will be lost; yet 1,000 units are generated in both cases. By which, then, shall we test the evaporative power of the boiler or of the fuel? clear that some other test must be supplied than the quantity of water evaporated; yet on this item alone do engineers dwell.

It is

For my own part, and on that of the sounder portion of the inventors, I assert that, in undertaking to effect a more perfect combustion of the gases in a furnace, as we do in the Argand lamp, I do undertake that the result will be a great addition of heat; but I do not undertake that the boiler shall give a commensurate increase of steam. To cure the disease of the furnace, does not imply the curing the disease of the boiler. If a physician be called in to cure one disease, his success is surely not to be estimated by the progress of a different one. It would be just as legitimate to determine the efficacy of a boiler by the work done by the

engine, as to decide on the merits of a furnace by calculating the work done by the boiler. The furnace is connected with the boiler, as the boiler is with the engine; but to determine the efficacy of the one by the power exercised by the other, would be contrary to all sense and science. Now, let us see how many circumstances are likely to interfere with the efficient action of both furnace and boiler.

Causes Influencing the Quantity of Heat Generated.-1. The state of the atmosphere, five to ten per cent; 2. The fire burning into holes, or unequally, and not attended to-five to ten per cent; 3. Irregular size of the coal lump, large and small-two to five per cent; 4. Inattention to removing the clinkers-five to ten per cent; 5. Variations in the draught and use of the damper; 6. Quantity of air admitted, and mode of admission.

Causes Influencing the Quantity of Steam Generated.-1. State of the flues,-clean or covered with soot; 2. Shape and size of the flues; 3. Extent of flue, or heat-absorbing surface; 4. Quantity of escaping heat,that is, the rate of current; 5. Temperature of this escaping heated matter by chimney; 6, Temperature in the flues.

Again, what are the terms and circumstances which should enter into our calculation in estimating the value or effect of any system, or any particular boiler? They are1. The weight of fuel employed; 2. The time taken for its combustion; 3. The quantity of heat generated; 4. The quantity of such heat absorbed by the water; 5. The quantity lost and escaping by the chimney,—that is, the current; 6. The temperature of the escaping products; 7. The weight of water evaporated.

In the case of the marine boiler experiments by Mr. Parkes, at times as much as 40 feet of the flue were filled with flame; and 12 feet of flame was the minimum. The flame from coke alone was never less than 10 feet long, and it became 20 feet when the fire was urged. Mr. Williams next ex plained a table, exhibiting the results of a series of minute and careful experiments, made by Mr. Josiah Parkes, on a marine boiler at Liverpool, during the preceding week.

[We propose giving the Table last alluded to by Mr. Williams, together with Mr. Parkes's report in our next.]

THAMES STEAMERS-MESSRS. SEAWARD AND CO'S. NEW ATMOSPHERIC ENGINE.

Sir,-Having read in your truly esteemed and useful work of the 25th instant, No. 985, an account of the successful trial of a