To remedy this, and also overcome the chance of the gate catching, two latches are here employed, one at the top and one at the bottom of the gate. This fastens the gate at once at both extremities. They are coupled together by a wire, so as to lift stimultaneously on pressure at the handle above. This gate weighs about 80lb., and can be made and put up for about 17. 8s., a price considerably under that which is ordinarily charged for common wooden gates.

Fig. 36. is a fan wire gate. Its skeleton is exactly the same in every way with that of fig. 35., only that the horizontal rail m n

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is omitted as superfluous. The wires which constitute the fan are fastened at their outer extremities by being driven up like nail heads at the point of their convergence they are screwed tight up by a nut. They at once improve the appearance of the gate, and make it so close as to be nearly game proof, while every single ray acts as a sustainer to some part of the bar. The curved segment into which they terminate, is a strong bar similar to that out of which the upper and lower rails are fashioned. A gate of this form was made to swing for some time to and fro, with a weight of 860 lb. at its extremity, and not the slightest alteration in its shape could be perceived: its weight is from 85 to 95 lb., and it costs from 17. 15s. to 27. The only person, the excellence of whose workmanship the inventor undertakes to warrant in following out the principles on which the wire gate is constructed, is Mr. John Douglas, blacksmith, Cupar, Fifeshire; although there is nothing in their form or structure which may not be executed by any ordinary blacksmith, so soon as he comes fully to appreciate the principle. Mr. Douglas is named as having been trained by the inventor. The same principle is equally applicable to toll bars as to park gates; and, indeed, is the more important in its uses the more extended is the span of the gate. Fig. 37. is a park gate with wickets on this plan. The span of the gate is 12 ft.; the wickets are 24 ft. wide, and 6 ft. high. The supporters may be made of open iron castings. The wickets could be made for about 18s. apiece, the gate itself for 47. or 5l. 10s. in all. A very small fraction indeed of the price commonly paid for park gates of similar appearance and show. It is not yet ten months since the first of these gates was put up;

and so much have they been in demand ever since, that Mr. Douglas had orders for betwixt thirty and forty of them, of which one was for Earl Gray, Howick Hall.

London, Dec. 1839.

[THE principles of construction exhibited in these gates may afford suggestions for combinations of iron wires and rods, to serve as skeleton roofing, upper flooring of cottages, and more especially for fire-proof flooring and roofing.- Cond.]

ART. VI. On the Management of Conical Boilers, with some Observations on the comparative Strength and Economy of different Kinds of Fuel. By JOHN ROGERS, Jun., F.R.S. F.H.S.

IN drawing up the description of the conical boilers, which appeared in the Gardener's Magazine for the last month, I purposely abstained from any minute details respecting fuel and management. Some experiments in which I was then engaged, on the comparative efficiency, as well as the relative economy, of various kinds of fuel being now complete, I proceed to lay the results of them before the public, premising my account with a few words on the general management of the boilers, in which, as the points touched upon are of material importance, I must run the risk of a little repetition.

In the first place, I wish it to be clearly understood, that no caking or bituminous coal, or indeed any coal which produces smoke, should ever be employed, except so far as a small quantity of coal will always be found mixed with good cinders. Partial inefficiency, or total failure, and an extreme waste, will assuredly follow every attempt to use improper fuel; and cinders, coke, or Welsh coal alone are suitable.

In the next place, the chimney should not, except under peculiar circumstances, exceed 5 ft. in height, nor should the aperture of it exceed that of the top of the boiler generally speaking, a chimney of about 3 ft. in height will be found most

convenient.

Lastly, it must be borne in mind that the furnace is to be filled full of fuel; and that the fuller it is kept, the more steadily and efficiently will it work. If allowed to get low, it burns too fiercely, and heat escapes up the chimney. On the other hand, the throat of the furnace must not be choked up, or the draught may be completely checked; a few days' experience is the best guide on this point.

One word of caution may be also necessary on the subject of clinkering and stoking. I am afraid some gardeners will be quite dismayed when they are informed that the last operation is altogether inadmissible. The fuel being thrown in at the top, falls by its own weight, and must never be either poked or stirred. When the bars are clogged, they are to be cleared from below with a hook, similar to those employed in Dr. Arnott's stoves, which is furnished with the boilers. If clinkers have formed, which will be easily detected, the aperture above the bars may be opened, and the clinkers dragged out, with as little general disturbance of the fuel as possible. Where Welsh coal is employed, no clinkers are produced, which is a great recommendation of this fuel. But, under all circumstances, the aperture above the bars should be closed, as directed in my former paper, and opened only to remove clinkers. I am particular in repeating this direction, because I know that many persons will disregard it, and will use this opening to stoke the fire; the consequence of which will be, that their fires will burn rapidly to waste, and the apparatus be rendered less efficient: nothing but absolute necessity has induced me to give them the opportunity of so doing, by adopting this opening in front.

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The following experiments were made with a 10-inch castiron boiler, of the form described in my former paper. It is set precisely in the manner there directed, with this exception, that instead of a chimney partly brick and partly iron, with a feeding-door in front, as there figured, my chimney is a mere cone of sheet iron, with a T-piece at the top, as shown in the annexed sketch. (fig. 38.) It is 2 ft. 9 in. high to the top of the T-piece, 8 in. diameter at the base, and 34 in. at the top. It is lifted on and off by hand; and, as it is never too hot to touch, if the fire be properly managed, it affords both a criterion of the management of the fire, and a proof that little heat is wasted by the chimney. It is light and easily moved, and its conical form prevents it from being easily blown off, of which there might otherwise be some danger. This boiler is attached to 44 square feet of radiating surface, in a small hot-house, 14 ft. by 12 ft. The heating pipes consist of 22 ft. of 4-inch, and 39 ft. of 2-inch, with a few feet of leaden connecting pipes, and a copper reservoir containing

45 gallons. The whole contents of the apparatus are 65 gallons, and the work performed by the boiler is about the amount which, on an average, I allot to that size.

It is unnecessary to detail, in a practical publication like the present, the exact mode of conducting the experiments. It is sufficient to say, that every precaution was taken to secure accuracy. The whole of the fuel being weighed and noted when put on, the temperature was ascertained by two self-registering thermometers, one in the stove, and one in the open air. The observations were made at 8 P.M. and 8 A.M., or nearly so; and the mean temperatures given are the mean of these temperatures thus noted, and of the minimum which occurred by night in the interval. The mean temperatures by night thus obtained, during the continuance of the experiments, are as follow:

The fuel employed in the first experiment was oven-burnt coke of the best quality, and cinders. The cinders were the ordinary refuse of the house, freed from dust and ashes by being sifted through a cross-wired iron sieve, having 16 apertures to the square inch, being one of the finest generally employed in gardens: every thing, therefore, larger than a pea, was retained as fuel; and such cinders are best adapted to these boilers.

The fire was lighted on February 10th, and continued burning for the fourteen days during which the experiment was continued. The attention it received and the ordinary management were as follows: Between 6 and 7 A. M. the fire was cleared, and clinkered if necessary, the fire-brick plug being taken out for this purpose; 4 lb. or one gallon of coke was then thrown in, and about an hour afterwards 9 lb. or one peck of cinders. This fuel lasted till 5 P. M., when the fire was again cleared and made up for the night, by the addition of 9 lb. or a peck of cinders. peck of cinders. Slight variations took place in the management, as occasion dictated. The first peck of cinders was sometimes put on at twice, when the fire happened not to be sufficiently burnt down to receive them at once: on some days rather more was burnt, as will be seen by the average. The excess of coke, however, there indicated, arose principally from a large quantity having been employed at first, till experience showed that it not only burnt to waste itself, but uselessly destroyed the other fuel. In a short time, the quantity above stated was found to be uniformly sufficient; and I have since

found that the coke is altogether unnecessary, and my boiler is worked with cinders only.

The average daily consumption of fuel per 24 hours on the whole experiment, was as follows: coke 64 lb., cinders 211⁄2 lb.; making a total of 27 lb. per day, say 28 lb., something under two thirds of a bushel.*

Having obtained a satisfactory average with coke and cinders, I next tried Welsh coal: the experiment in this case was continued for seven days. 6 lb. of coke were employed on the first day in lighting it; and it took, in addition, 38 lb. of Welsh coal to fill the furnace, and get up the heat, as the water was nearly cold. After this, 19 lb. per twenty-four hours was the regular consumption; of which 8 lb. were put on about 7 A. M., and 8 lb. about 5 h. 30 m. P. M. The fire, of course, never went out during this period; indeed, not one third of the contents of the furnace was consumed in the morning.

Nothing can surpass the efficacy of this fuel: it burns entirely away without any waste; it produces neither clinkers nor smoke; and, upon an accurate calculation, the total waste by the chimney does not exceed 23 per cent of the heat produced; and it is more durable than any other fuel. The only precaution necessary is to break it to pieces about the size of eggs, or rather larger, using it dust and all together. As it produces no clinkers, there is no occasion to take out the fire-brick plug; and the only attention requisite is to clear the bars two or three times a day; but even this is scarcely necessary if the apertures of the bars be sufficiently large, as the coal burns entirely to dust. I find, however, that it requires rather a stronger draught than other kinds of fuel; so that, where it is to be permanently employed, the chimney should be half as high again as I have recommended above; say 4 ft. 6 in. instead of 3 ft.

It will be gathered from the foregoing details that coke, by itself, is not a suitable fuel for these boilers; unless, at any time, it be necessary to produce heat very rapidly. That which I employed is of the best and strongest quality; but, nevertheless, all coke being coarse and very porous, allows an excessive draught, and burns away rapidly, wasting much heat by the chimney; and, even if this evil could be obviated, the fuel itself being so very light, the furnace will scarcely contain enough to last twelve hours. Its specific gravity is about half that of Welsh coal; my peck of coke weighed 8 lb., of Welsh coal 19 lb.

Where fuel is to be bought, unless good cinders can be

My bushel of coke weighed 34 lb., of cinders 38 lb.; but, as the quantities were taken with a gallon measure, the bushel was, I believe, a very short one. I understand 40 lb. is the average weight of oven-burnt coke. I presume, therefore, my cinders weighed about 45 lb. to the bushel; but I have given my quantities by weight, instead of measure, to preclude mistake.