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sity of cleaning the flues, but to render their capacity of imbibing warmth from the current of heated air at all times equal. Wherever a white heat is constantly produced, there can be no difficulty in burning the smoke; but as hóthouse fires are generally half the day either extinguished or nearly so, it may be pronounced as impracticable to produce any scheme that shall completely effect this purpose. There are however two modes, which approach perhaps as near to the attainment of this desirable object, as the above circumstance will admit of; the one is by the Marquis de Chabannes', and the other by Mr. Robertson?. In both the fuel is supplied from a hopper placed over the furnace; but that of Robertson has an air valve which renders the consumption of the smoke more complete than in those of Chabannes, which indeed are more calculated for dwelling-houses. Hopper furnaces have but in very few instances been tried in hothouses 3; but I have little doubt of their being found real improvements, and especially if connected with the regulating apparatus already repeatedly mentioned 4.

Mr. Nicol, rather than run any risk from new plans of furnaces, or any improved æconomy of heat and fuel, recommends a large fuelchamber, and the fire to be well heaped up with ashes at night, so as to keep up a constant circulation of smoke in the flues till the morning. And considering that whenever any accident happens to the house through the carelessness of the attendant, the blame is without fail attributed to the new plan, whatever that may be, this reconmendation

may

be considered as of practical utility.

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· Explanation of a New Method, &c. p. 21, in which the calore fumivore is described. * Rees's Cyclopedia, art. Steam.

A hopper furnace joined to a boiler is described by Mr. MoNaught in Buchannan's Treatise on Heating, &c. by Steam, p. 197; but the most improved plan which I have seen for a fur. nace and boiler is that adopted by Mr. Fraser at the Royal Gardens at Kensington.

* There are various ingenious plans for consuming the smoke in grates by Franklin, Cutler and Co., Begbie and Dickson, Hawkins, and some others, attended with different degrees of suc

See Repertory of Arts. Forcing Gardener, 3d edit.

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, Justice, Bénard, Weston, and Dr. Anderson have proposed using lamps for supplying heat; but it is evident their use for that purpose must be very limited.

Ventilation has hitherto been very imperfectly performed in hothouses, especially during the winter season, and in close foggy weather. Boerhaave, Linnæus, and Adanson made complaints on this head in their times; and an excellent practical gardener (Mr. Mean) in the last edition of Abercrombie's Practical Gardener just published states that“ a good mode of ventilation is still a desideratum." Linnæus caused a stove to be erected in the centre of his Caldarium at Upsal, in order by occasional fires to purify the air of the house when the severity of the weather did not admit opening the sashes. The Dutch generally used their back sheds as reservoirs of temperate air, to be interchanged with that of the house by means of doors and other apertures in the partition, or, as it is liere generally termed, the back wall. Quintinye and the editor of the third edition of La Nouvelle Maison rustique propose large porches or antechambers at each end of the house for similar purposes, the doors to which might act as fans every

time any person entered the house', or the constant admission of heated air by means of Gouger's fire-places?, which act much in the same way as the mode of ventilation adopted by Sir Humphry Davy in the House of Lords.

Hales proposes using the same machine which he applied so suc

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Chaque fois qu'on entrera, cette antichambre, par laquelle on puisse passer pour entrer dans la serre, se fournira d'uir nouveau ; et ouvrant après la porte de cette antichambre qui donne dans la serre, l'air de cette antichambre se mêlant avec celui de la serre qui est usé, lui donnera les parties nécessaires qui contribueront à la végétation et à l'acroissement des plantes. -La Nouvelle Maison rustique, Rouen 1768, tom. ii. p. 14.

On peut pourtant faire usage des chéminées inventées par M. Gouger, dont l'avantage est qu'il entre suns cesse dans la serre, de l'air nouveau également échauffé, et que l'uir qui y est renfermé en sert aussi continuellement, &C.-Ibid. tom. ii. p. 15.

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cessfully to ships', of which Bradley takes notice, and offers some additional hints as to its application. Dr. Anderson, however, has treated the subject most at length. He proposes reservoirs under or adjoining the house, to be filled with the superfluous heated air generated by the sun in the day-time, and to be used as occasion might require both for the purposes of ventilation and heating. “For the purpose of agitating the air of the house at pleasure, without the necessity of introducing air from without,” he proposes to place a fan like that of a winnowing-machine in a cylinder so arranged as to “suck up

air from any part of the house at pleasure”, or if desirable from without, and “spout it out on any other part of the house with a greater or lesser degree of violence.”. Dr. Anderson's ideas on the subject of hothouses were unfortunately never systematized and reduced to practice; though all of them admit of adoption under certain circumstances. His treatise on the patent hothouse is replete with the most ingenious ideas and reasonings, which, as is too often the case, will probably long remain hid till called forth by some pressing necessity, or individual interest.

Mr. Stuart in the Specification of his patent does not propose to agitate the air of the house, but to refresh and cool it down to the requisite degree, by admitting air through tubes, which commence with a funnel or trumpet mouth on the surface of the ground, outside the house, and end in a perforated plate covered with a regulating valve near the upper part of the inside of the house. The light wasted air is allowed to escape by tubes commencing at different heights from the floor, and terminating outside the roof. In this arrangement there does not appear a sufficiently powerful and active principle of motion; for no fluid is so sluggish as air.

Mr. Strutt of Derby has adopted a plan in ventilating his house which merits adoption in many cases. A tube with a funnel mouth,

On Ventilation, London 1743, p. 24.

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contrived to turn to the wind, commencés one hundred yards from, and is conducted under ground to, the house; this supplies temperate air in winter and cool air in summer to all the different apartments, A tube on the root, with a funnel contrived to turn with the wind, draws off or adınits the escape of the wasted air from the different apartments. The same plan is used in the Derby Infirmary. In Mr. Strutt's house, the air on its introduction in the ground floor is heated by flues under the different floors of the first story. The whole ara rangement in regard to heating and ventilating, no less than as to the fitting up of the kitchen and offices, is unique, and is, or was in 1811, the most complete in England.

The Marquis de Chabannes' principle of ventilation for private houses, and which he proposes to adopt also in hothouses, bears a near : resemblance to Mr. Strutt's. He places a ventilator, which he calls an air pump, at the top of the house, to draw off by means of tubes communicating with the cielings of all the rooms in the house, the rarefied air; and at the bottom of the house he has a recipient or room, which in winter may be filled with hot air, and in summer with cold air, also communicating by tubes with the lower part of all the rooms. The tubes are of course furnished with valves, so that the temperature of each room may be regulated at pleasure. The air. pump is kept in motion by wind, or by the smoke of the kitchen chimney after the manner of a smoke jack. It is evident that, as the air pump draws off the air, its place must be supplied from the tubes communicating with the lower recipient, unless the windows or doors are open. This arrangement certainly admits of modification, so as both to serve for heating and ventilating hothouses; but the heat

pro. duced from hot water or steam being so greatly preferable to that produced directly from ignited fuel, and the action of the air pump, when there may be little or no wind or smoke, being rather doubtful, I am inclined to think a greater degree of perfection is to be expected from the mode proposed by Mr. Benford Deacon, with the improvements of which that mode is susceptible.

For warming and ventilating, Mr. Deacon' heats his air in boxes or chests of highly-glazed pottery tubes, or in boxes of tubes, or, double plates, or cellular masses of cast iron, immersed in a vessel of boiling water. To convey this air to the house, he employs a fan fixed in a semi-cylindrical machine, placed in the lower part of, or any where near, the house. With this machine he draws up the air of the atmosphere, forces it through the box of immersed tubes, where it receives the requisite degree of warmth or coolness, into a main communicating by tubes with the different rooms to be heated and ventilated. In ordinary cases, the fan-machine may be kept in motion by a jack or other similar engine; on a large scale, as for heating or cooling churches, &c. by manual labour. For cooling and ventilating, the air is drawn through a dry drain, or from a cool cellar, and the box of tubes is immersed in cold water, &c.

By distributing the conducting tubes under the floor, or even under the paths only, of a hothouse, and perforating them so as the heated air might rise as equally as possible, or by using tubes of canvass or woollen netting, and by leaving unputtied the interstices between the

panes of glass; a very simple and, as it appears to me, a very perfect mode of heating and ventilation would be produced. It might of course be regulated at pleasure, and used either with or without the aid of smoke flues or steam tubes. In a large range, the boxes of tubes for heating the air might be immersed in steam, under or behind each house; and one fan, and one fire and boiler, erected in a centrical situation, might produce the whole effect. The arrangement would be such, that if by accident or want of fuel the fire got low, (though with a hopper furnace this could hardly happen,) then the motion of the fans depending on the force of the steam, the quantity of air driven through the box of tubes would be lessened in

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Specification of Patent 1812. These machines, which the inventor calls Æolians, are erected and answering the proposed ends at the Old Bailey, Albion Tavern, and Valpy's Printing-office. One will shortly be erected in a greenhouse at Streatham,

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