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and deserves trial in all private gardens where early forcing is an object.

In respect to the boxes or wooden frames, the only general improvement made in their construction is that of keying them together, instead of making permanent joints; by which means they may be taken to pieces and preserved dry, repainted, &c. when not in use'. Cast iron frames have been tried, but are too powerful conductors ever to answer the purpose.

With respect to the glass frames of hotbeds, Mr. Henderson?," in order to increase light and heat,” has "adopted a construction which may be termed the triple meridian sash." The glass is raised in the manner of a pavilion roof, presenting three planes; one exposed to the east for the morning sun, another to the south for that at mid day, and a third to the afternoon's sun. Mr. Henderson built his hothouses on the same principle, with glass on all sides and their ends to the south, as in the range in the Dublin Society's gardens near Dublin, and after seven years' trial he finds this plan answer his expectations.

I have tried one sash of this sort here, together with another in which the glass is in a semicuneiform shape, the section of the obtuse end being semicircular, which effects more completely the same object. I have also tried a sash glazed in the ridge and furrow manner, with grooves in the furrow astragals, which some excellent practical gardeners are of opinion will increase the effect of the morning and afternoon's sun, and totally prevent the water of condensation from dropping on the plants.

Various modes have been tried or suggested for supplying heat to hotbeds without the aid of dung, some of which have been hinted at; such as cast iron boxes of the same size of the hotbed, filled with hot water obtained from a distillery3 or other manufactory, or from a hot

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spring; by metallic reflectors to concentrate the calorific rays of the sun'; by collecting the sun's heat in reservoirs, &c. &c. In addition I shall suggest to the curious the idea of employing the chemical agency of calorific or incanescent mixtures3, the mechanical effect of compressing air in cast iron boxes or tubes1, and the absorbent effects of black substances, such as troughs of pitch, powdered coal, soot, &c. during sunshine, and which shall radiate a sufficiency during night and in his absence to keep up the temperature of the air of the hotbed.

HOTWALLS seem first to have been adopted by the Duke of Rutland at Belvoir Castle, about or before 17105; since which time they have become very general in the north of England and in Scotland. In respect to the mere construction of, the wall there has been little or no improvement; nor at first sight do they seem to admit of much in that respect; but numerous varieties of screens, or protections from frosts and dews, have been invented, and applied with considerable degrees of success. Frondiform branches of the evergreen fir tribe, straw ropes placed at regular distances?, mats of straw, reeds, bark, or rushes, boards placed horizontally and perpendicularly9, oiled paper

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1 Buth Society's Papers.

Sulphuric acid and water, for example.

As a certain proportion of sulphur, iron, and lime, &c.

* Mr. Dalton has estimated that air compressed to half its dimensions has its temperature elevated to about 50 degrees. Hence it may be inferred that a condensation equal to 1-180th of the bulk of any portion of air will raise its temperature one degree. When air is very rapidly condensed in the condenser of an air gun, it is sometimes so much heated as actually to set on fire a small portion of tow placed near the end of the barrel.-Young's Lectures, 39. p. 632. • Laurence's Fruit Garden Kalendar, edit. 1718. Introd. p. 22. Switzer's Practical Fruit Gardener, edit. 1724, art. Wall.

Niel On Scottish Gardens and Orchards, art. Hotwalls.

'J. Laird in Caledonian Hort. Trans. vol. i. p. 342.

Edinburgh Encyclopedia, art. Horticulture, sect. Preserving of Blossom.

? Laurence in Fruit Garden Kalendar, &c.

frames, canvass frames, and other contrivances, have been used for this purpose; but the regular systematic construction is curtains or blinds of oiled bunting, Osnaburg or coarse woollen netting' attached to the projecting coping to be let down or drawn up at plea

sure.

The object of hotwalls being more to mature the young wood and fruit in the autumn, and to protect the blossom from frosts in spring, than to force or procure premature vegetation, the latter object has been successfully attempted by covering the trees with boards or branches, so as to exclude the sun in the day-time, and exposing them at night. This practice is common in the north of Europe, and I would suggest from it the following idea, for very early forcing of grapes or peaches. Grow the plants or trees to be forced in pots or boxes, and retard vegetation during the whole of the summer previously to the winter you intend forcing, by keeping them in an ice. house. Take them out in the autumn or beginning of winter, say in October, after having been there twelve months, and place them in a hothouse of suitable temperature, &c. It is probable with judicious management any sort of fruit might be thus obtained from January till the usual season of forced fruits; in short, with a pinery and a large ice-house any person might thus gather ripe grapes, peaches, apricots, apples, pears, cherries, gooseberries, strawberries, &c, &c. every day in the year. Whether any thing could be done in aid of this plan by employing frigorific mixtures in air-tight sheds or cel

Edinburgh Encyclopædia, art. Horticulture, sect. Preserving of Blossom.

• On the 20th April, 1814, there were in the hothouses of the Imperial gardens at Tzaritzina near Moscow, ripe apples, pears, cherries, plums, gooseberries, raspberries, and strawberries, and most sorts of salads, roots, legumes, &c. fit for use, such as parsley, lettuce, carrots, turnips, potatoes, pease, &c. The open ground had been covered five months with snow, and was so till about the first of May. On the evening of the 1st of June, the eve of my departure from Moscow, there was a fall of snow which covered the ground nearly two inches. If in such a climate the art of forcing is so far advanced, what may not be done in this country, where we have so much more sun during our short winter?

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lars, instead of resorting to icehouses, might easily be tried; and from Professor Leslie's recent experiments with powdered granite, at very trifling expense.

I have already mentioned some of the advantages to be derived from a zig-zag wall as a common garden wall (p. 32)1, and I have now to suggest the idea of employing a double wall of this description as a hotwall. By the double wall a vacuity would be formed capable of being either heated as one large vertical smoke chamber, or divided horizontally so as to be formed into flues, and heated in the usual way. The trees would be trained on a trellis formed by stretching wires horizontally along the wall at the distance of the thickness of two bricks, and fixed to the salient angles of the zig-zag work. The advantages of this disposition of trellis and wall would be very considerable. Independently of the advantages of a double meridian already mentioned, the heat radiated during night from the two sides of the wall in the rentrant angles would be reflected back, and prevented from escaping by the two brick sides and by the trellis forming the third side of this triangle--from the body of air contained in this triangle the flavour of the fruit will be rendered superior to that of those grown on common walls, in as much as it will approach nearer to that of standard trees which is surrounded by light and air on all sides: and from no part of the trees touching the wall no heat of the flues can ever injure them. The œconomy of this construction is also a considerable recommendation, since a double wall as above described will not require many more bricks than a nine-inch wall, whereas hotwalls are in general built twenty-four inches and

Miller in his Dict., art. Wall, and Robinson in his Collection of Designs for Stoves, &c., London 1791, description of plate 22, mention, and at the same time disapprove of, angular walls. But as the angles in the walls to which they allude were intended to be so large as that each side might contain a trained tree, there would be no saving of materials in constructing them. These walls, indeed, both in construction and principle are radically different from the zig-zag wall; the object of the former being different exposures; that of the latter, to save expense and retain heat with the same exposure as that of a common wall..

half wide. If an extensive range of such walling were to be heated by steam, the best mode, would be to leave a vacuity from the bottom to the top of the wall, and to lay one cast iron steam tube along the bottom of the vacuity. In this way, whatever might be the extent, even if the whole of the wall surrounding a garden were double, it might readily be heated from one boiler1.

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Inclined walls might be built hollow by either of the three modes mentioned in a former part of these Remarks (p. 31): no more bricks would be required for every yard in length of a wall inclined to an angle of 50 degrees, than are now required for every yard of a solid fourteen-inch wall. They might be heated by steam in the manner proposed above for a hollow vertical wall, and in all cases there should be a curtain of woollen netting to be let down early in the afternoon, and pulled up only during rain and sunshine3. A sloping wall praperly arranged would be a very excellent substitute for late forcinghouses.

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The hothouses in Messrs. Loddige's nursery now heating by steam form two parallel ranges of 500 or 600 feet each. It is intended to join these sides by ends of 200 or 300 feet each, thus forming a continuous parallelogram of glass, the whole to be heated by steam, and from one boiler. When finished it will be the most extensive thing of the sort in the world, and highly creditable to these gentlemen both in respect to design and execution. The idea of adopting steam Mr. Loddige received from Mr. Massland of Stockport, who has adopted it extensively in his hothouses, as has Mr. Knight, the President of the Horticultural Society, in a house recently erected at Downton Castle.

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For their advantages see Facio's work formerly referred to. As far as I have been able to learn, there are only two copies of this book in London; one in the library of the Royal Society, and the other in that of Sir Joseph Banks, to whose liberality I am indebted for the perusal of this, as well as several other scarce works referred to in these Remarks.

• One variety of Mr. Kewley's machine does not go so far as to regulate the temperature, but simply indicates by sound what ought to be done. It consists of a thermometer which rings a bell or an alarum when the mercury rises or falls to any particular degree, or at any temperature at which some operation requires to be performed by the gardener. Such a thermometer might be placed on the hotwall, and the index put to the proper degree according to the season, &c.; so as to ring for the gardener at the exact moment when the curtains are to be let down in the afternoon. A similar thermometer in the open garden might indicate the proper time to draw them up or uncover in the morning. The uses to which the forcing gar

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