one of these boilers to the council of the Horticultural Society, and its merits were satisfactorily proved in the Society's Garden, and made known to the fellows, and ultimately to the public at large, through the Gardener's Gazette, Gardener's Magazine, Paxton's Magazine of Botany, and other periodicals, all of which overlooked the original inventor so far as to allow him no share of the merit of this very useful invention.

The boiler is yet susceptible of improvement. In its present form it is made up of two concentric cones, joined at top and bottom by flanges sufficiently wide to leave a space of one or two inches between them for the water. The fire is applied in the inner cone. There is a defect in the outset, which is soon detected in practice. As soon as the fire begins to burn clear in the inner cone, the heat is generated faster than the small body of water can absorb it, and steam is soon produced. There is a small pipe fixed in the top of the boiler with a steam valve to guard against accidents. By close attention to the fuel and damper, this steam might be avoided, and only as much heat produced as could be absorbed by the water; but this requires too great a nicety for so simple an apparatus. Instead of having the inner part of the boiler a cone, let us have it more of a cylindrical form: this would reduce the size of the fire and the surface to be heated, and it would increase the space for the water in the same ratio. Probably some modification of this kind would simplify the working of the boiler by producing no more heat than is absorbed by the water. At any rate, we must get rid of the steam, at least till the water in all the pipes is heated to 200°.

It were desirable that those who use this boiler, and think they could suggest any improvements, would convey their ideas to Mr. Shewin, as above, or to some other enterprising ironmonger or engineer, in order that we may have the benefit of this most excellent invention to the fullest extent. The very great saving in fuel, the almost entire absence of smoke, and the ease with which it can be attended, will cause it to supersede all other forms of boilers now in use; and there is no reason why it should not be made sufficiently large to suit houses of any size. An article, like this boiler, which must soon come into universal use, will, no doubt, be taken up by several tradesmen for the sake of profit, and severai modifications of it in consequence

was an invention to which Mr. Rogers was led by a series of experiments founded on certain principles, and having a certain object in view. Mr. Rogers tried a vertical cylinder first, which did not answer perfectly, wasting much heat. He then employed a cone, which succeeded better. But for Mr. Shewin's perseverance in accomplishing the object in cast iron, it is doubtful whether it would ever have become of general service; as Mr. Rogers's original boiler was made of copper, which was much more expensive, and, as it proved, much less durable, than iron. — D. B.”

will soon be before the public; it is therefore but justice that Mr. Hogg, the original inventor, should have his share of the merit.

I suggested to Mr. Shewin this week to make small boilers, or rather steamers, on this principle, for steaming houses and frames in summer, when no fires are at work, and for smoking houses or frames by the steam of tobacco liquor; or by a decoction of common tobacco leaves. This is a novel plan for destroying insects, but I am fully satisfied it would answer better than the present mode of smoking. The vapour would condense and fall down on the plants in the form of dew, whereas smoke soon finds its way out at every crevice. Many other decoctions or solutions might be tried in this way, for the destruction of scale, bug, or even wood-lice, when something effectual for the destruction of these creatures might be found out, and on which the operative chemist might try his ingenuity. I saw a vessel in shape between a tea-kettle and watering-pot used for steaming houses twenty years ago. Many other contrivances for the same purpose have been tried since, and found to be very beneficial; that by Mr. Forest, at Syon Gardens, is very effectual; but this by the conical boiler is the simplest and cheapest that can be used. A gentleman in this neighbourhood used a most elaborate and expensive machine for the same purpose last summer, and with perfect success. The conical boiler, for these purposes, should have the inner or furnace part in the form of a cylinder, from 6 in. to 10 in. wide, and from 10 in. to 14 in. high; the outer part may either be a cylinder or cone, at pleasure; the top should screw on, and have a short pipe fixed in it for filling it, to which another pipe of the required length, and with a universal joint, should be fixed for conveying the steam into the house or frame, which might be done through a pane of glass in front, or in any other way more convenient. A movable sheet-iron box should be attached to the bottom to receive the ashes, and the whole might be mounted on a barrow similar to that of a small watering engine: such a boiler or steamer might be got for 40s. or 50s., and it would last two or three lifetimes if properly taken care of. What a nice plan for smoking or rather steaming cucumbers, melons, and heaths, which do not like smoke! I hope Mr. Shewin will attend to these suggestions: every one having house-plants would soon possess one. It might even be taken to the peach wall; and, by means of the universal joint, a stream of tobacco steam could easily be directed against all parts of the trees; and the same way with standard roses, &c. By the same means a house could be filled with any sweet odours, to keep down any disagreeable smell from tan, dung, flues, &c.; but I believe I have said enough in its praise to draw public attention to it.

Kingsbury Gardens, Jan. 1840.

ART. XII. Description of the Conical Boiler and hot-water Apparatus invented by John Rogers, Jun., Esq., F.R.S. Communicated by Mr. ROGERS.

I HAVE much pleasure in furnishing you with a description of my conical boiler, of which you are pleased to express so favourable an opinion. The apparatus, as at present constructed in cast iron, is the result of a series of experiments, which have engaged my attention at intervals during the last five years. My first attempts were made in 1835, with a cylindrical boiler of tinned iron, of which an account was published in Paxton's Magazine of Botany, for March, 1836. The experience thus attained led me to adopt a conical instead of a cylindrical furnace; and, in a paper published in the same work, in March, 1837, my boiler had assumed very nearly its present form. Various difficulties, however, arose in the construction of the apparatus. Copper, the material which I had employed in my second boiler, in the hope that it would prove durable, was corroded in a few months, by the sulphur disengaged from the coke; while the expense and difficulty of casting such peculiar forms in iron deterred me from employing that material, especially as it was a matter of considerable doubt whether its unequal expansion would not cause such a boiler to break, or become leaky. At length, after some other unsuccessful experiments which it is unnecessary to detail, the ingenuity and perseverance of Mr. Shewin, an ironmonger of this town, have succeeded in overcoming the difficulty of casting in iron, and a boiler has been produced which combines strength and solidity with the advantages previously attained. The only point in which the iron is inferior to copper is, that the greater thickness of the metal does not allow the heat to be transmitted from the fuel quite so rapidly. In practice, however, this is scarcely perceptible, and is far more than compensated by the superior strength, economy, and durability of the iron boilers. Indeed, I believe that those in copper could never have been made generally useful; for, besides their liability to wear out, on which experience a little varies, they were very easily injured by rough usage.

As many of your readers are probably unacquainted with the apparatus, I shall endeavour to give a description of it in its present form, with such plans and particulars as may enable them to judge how far it is applicable to their purposes, and, if necessary, to erect it themselves.

Fig. 23. is a front view of the boiler as at present constructed in cast iron. The interior, a sugarloaf-shaped cone (indicated by the dotted lines), being the furnace, which is filled with fuel through its upper orifice (a). A circular fire-grate is fixed just within the bottom of the boiler; and the aperture b, seen in

front is intended solely to remove clinkers which may form, or fuel when the fire is extinguished; at other times it is closed with a firebrick plug, and should never be opened except when absolutely necessary. My original boiler had no such opening, and was fitted with a revolving grate, which overturned to empty the furnace; but various inconveniences, and the frequent breaking of the pivots on which the gratings swung, have led me, somewhat unwillingly, to adopt the present alternative.

For a side view of the boiler see fig. 26., where it is represented

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as attached to a range of pipe. f and r are the flow and return pipes, and d a flange for examining and cleansing the boiler when necessary. Into this flange is fixed a small pipe, which, being connected upwards with the supply cistern e, and downwards with the cock or tap h, serves to fill and empty the apparatus. The supply cistern (e) acts also as an expansion cistern, to receive the volume of water increased by heat.

Fig. 24. shows the most convenient mode of setting the above, exhibited by a front view. A solid base being built with an

aperture in its centre open to the front, as high as the desired depth of the ash-pit, the boiler is fixed upon it, and the brickwork carried up to its lower flange or rim. The side walls should then be raised, in 4-inch work, level with the top of the boiler, as represented in fig. 24. a is the ash-pit; b the boiler; c the aperture in front of the boiler, closed with fire-brick; e e and dd

two bars, one supporting the fire-brick plug, and the other fitting to the rim of the boiler to support a slate which closes the front as in fig. 24. ff (fig. 22.) is the chamber around the boiler, filled with sawdust as a non-conductor of heat; and a layer of sawdust extends over the top of the boiler, under the slate slab gg, which is fitted over the brickwork, an aperture being cut in it to allow the throat of the furnace to pass through.

Fig. 25. gives the same view farther completed: the front of the chamber is closed with a slab of slate, and on the slab which covers the boiler is erected a chimney, having a feeding-door, through which fuel is supplied, placed in its sloping face directly over the mouth of the furnace. This chimney must not exceed 4 or 5 feet in height, and its area must in no case exceed the area of the mouth of the furnace. That here represented, viz. a brick base, with a piece of 4-inch iron pipe about 3 ft. in length, will probably be found most convenient, unless a movable chimney be preferred. This chimney should be fitted with a damper just below the iron part, to give greater command of the draught. The aperture of the boiler, which is closed with fire-brick, and the front of the ash

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pit, should also be closed by a door or blower, having a regulator to admit or exclude draught. A blower is preferable to a door, as hinges are always liable to rust, and then break or strain; and it is important to be able to close the ash-pit pretty accurately.

Fig. 26. shows the relative position of the boiler and pipes, and the mode of attaching and arranging them. In the first place, the whole of the pipes should, if possible, be above the boiler. One foot is sufficient, but when convenient, the higher the better. When 2- or 3-inch pipe is employed, the pipes may rise uniformly about 1 in. in 20 ft. from a and b to c; on which, being thus the highest point of the pipes, an air-cock is placed. But, if 4-inch pipes be employed, it is better that a should be the highest point, and the air-cock placed there; and that the pipes should fall uniformly 1 in. in 20 ft. from a to c, and from c to b: indeed this is generally the best arrangement, where not inconvenient. From b the return-piper should descend either perpendicularly, or with