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compartment flues'; but both these modes of increasing the surface to be heated, are liable to the objections of retarding the progress of the smoke, and consequently of accumulating, the heat too much at the end next the fire; besides rendering it impossible to clean them without adopting the abominable practice of introducing boys for that purpose. Mr. Lorimer found can flues answer, which Dr. Duncan3 is inclined to think a serious improvement. They have been long in use more or less both in Britain and on the continent. As they are soon heated and soon cooled, they are not to be depended on for a regular temperature, especially in the night-time; but being œconomical, of easy carriage and readily put together, they deserve adoption in several cases, and especially under temporary glass roofs placed against hot walls. When used in permanent houses they should be wholly or partially immersed in coarse sand as in Holland, by which means their characteristic defects are in a considerable degree remedied. From forming a more perfect tube or funnel than a brick flue, it is probable the heat given out by can flues will be more salutary than that emitted from those constructed of the former material; from the numerous joints of which smoke and decomposed air sometimes escape to contaminate the atmosphere of the house. In connexion with an outer or inner curtain, which will prevent any house from cooling in one night to a pernicious degree, I should have no hesitation in adopting them generally, as being cheap, simple, easily transported and erected, and less liable to the objection of Sir Joseph Banks, that of "wasting in the walls which enclose them half the warmth they receive from the fires which heat them."

'Short Treatise on Hothouses, sect. ii. p. 33.

* Caledonian Hort. Trans. vol. ii.

Caledonian Hort. Trans. vol. ii.

⚫ At Duddingston House, Edinburgh, in 1790; Dalry, 1795; Stoke Newington, Middlesex, in 1789. Adams and Co. potters, London, have sent them to various parts of England for hothouses during the last twenty years. Their use is described for serres à fruits in Encyc. Méthod. and N. Dict. Economique, Paris, an ix. See also Kirchner's Practische Anleitung für Gartenkunst, &c. Leipsig 1796.

Sir George Mackenzie has lately' suggested a plan of heating hothouses by an open fire place, built within and near the centre of the house, and with flues proceeding from it towards each end, &c. Sir G. is sanguine as to the success of this notion, and it must be confessed there is something social and comfortable in the idea of seeing one's plants surrounding a bright fire; but it may be doubted whether the local force of this radiating heat, its drying effect, and the dust which is thrown out by the best (even Raffele's) grates, would not counterbalance any advantage which this plan may possess in other respects. The immense conservatory attached to the palace of Taurida at Petersburgh is heated nearly in this way; but as it contains chiefly orange trees, and as wood is the fuel made use of, one can hardly judge from it of the effects that would be produced by coal fires among vines or tender exotics in this country.

The original construction of furnaces has been somewhat improved, by hollow bars to promote durability3; by double doors to the fuelchamber, so as to prevent any air from being drawn in along with the smoke, that has not by entering through the ash pit door passed through the fuel and become heated; and by a door to the ash pit, and a damper near the chimney top, by shutting either of which when the fuel is thoroughly ignited, the hot air is stagnated in the flues, which thereby remain much longer in a state to give out heat to the house, than would otherwise be the case.

Various attempts have been made to consume the smoke in hothouse furnaces, so as to obtain more heat from the fuel, and by keeping their inner surface free from soot, not only to prevent the neces

1 Caledonian Hort. Trans. vol. ii.

The orange is particularly hardy. Quintinye (Jardins Fruitiers) says they require little or no heat in France; and Humboldt observes (De Distributione geographica Plantarum, Paris 1816, p. 158), that though the orange requires at an average in the open air 17 degrees (64° of Fahrenheit), yet it will resist a cold of 7 (45° of Fahr.) if it last only a few hours at a time. Bradley's Patent, see Repertory of Arts, vol. xii. New Series.

Count Rumford first introduced double doors to hothouse furnaces.

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 hothouse 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 hothouses3 ; but I have little doubt of their being found real improvements, and especially if connected with the regulating apparatus already repeatedly mentioned.

Mr. Nicol, rather than run any risk from new plans of furnaces, or any improved œconomy 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 recommendation may be considered as of practical utility.

1 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. McNaught 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.

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⚫ 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 sucSee Repertory of Arts.

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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 here 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.

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Hales proposes using the same machine which he applied so suc

Chaque fois qu'on entrera, cette antichambre, par laquelle on puisse passer pour entrer dans la serre, se fournira d'air 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 sans cesse dans la serre, de l'air nouveau également échauffé, et que l'air 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 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.

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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 requi site 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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