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cutters. It is chiefly adopted by nurserymen and market gardeners for the sake of economy, as quantity and bulk are more their object than flavour. As the angular forms are generally brought in so as to throw the water on the astragal, the lap admits of being entirely puttied up; which is essentially necessary in cucumber frames on account of the increased number of interstices, which would otherwise cool too rapidly their small volume of heated air.
Common glazing with a leaden lap. The common form of pane, but placed in one plane and joined, not by the panes lapping over each other, but by the intervention of a lap of lead, a, which projects over them reciprocally on both sides. This method about twenty years ago was a good deal in use. In flat roofs it is apt to admit the wet; but when applied to ridge and furrow sashes, or to panes cut diagonally, or in the form of rhomboids, it is of considerable use.
Rhomboidal glazing. Fig. 7. This is a very good mode, especially if a metallic lap be used, as in place of leaving the condensed water to run down the glass it throws it on the astragals. It has been chiefly used by Mr. Stuart in connexion with a very ingenious met tallic lap invented by him; the origin of which may be recognised in the shred of lead which glaziers sometimes introduce between newly glazed panes to retain them in their places (see b). This lap adds greatly to the strength of hothouse glazing, and may be considered as preferable to all other modes for preserving the glass from being broken. It is generally made of copper; but in hothouses ought to be manufactured from some ductile compound of metals not obnoxious to rapid oxidation.
Perforated shield glazing. Fig. 8. This mode and that of Fig. 7 are obviously derived from Fig. 6. The interstices are puttied, excepting a space of about half an inch in the centre, to which the condensed dews are naturally thrown, and these pass to the outside of
the glass. Mr. Jorden has taken out a patent for this mode, which he calls“ perforated shield glazing!,” and he states that he uses a hard putty in the interstices of the lap, in which he forms a groove for the water, &c. It has nothing to recommend it, but the novelty of its appearance; for, by the perforation in the upper part of the shield, the dexter and sinister chiefs are liable to be broken off; and by the acumination of its base, it is rendered obnoxious to the same casualty in the nombril point.
Entire shield glazing. Fig. 9. The shield being entire, of course where the chief of the one overlaps the base of the other, a space of double glass will be formed in the junction in the form of an isosceles triangle. This space is puttied up, excepting two openings of about half an inch each at the sides for the escape of the water, and to which it is thrown by the acumination of the inverted base of the shield. This mode is much stronger than Fig. 8; but the opaque triangular space gives it a heavy appearance, and in fact excludes a good deal of light. It is used by Mr. Butler, a respectable wooden hothouse builder, and may be seen in the house erected by him for Mr. Palmer at Kingston before mentioned.
Common glazing with a circular lap. Fig. 10. This has all the supposed advantages of Figs. 8 and 9, without any of their numerous disadvantages. It has been long used by Mr. Miller, a respectable glazier in Swallow-street, and may be considered for common purposes as preferable to all others with the lap half puttied; or, in connexion with an outer roofing, with the lap open.
Glazing with the circular lap reversed. Fig. 11. This is merely the reverse of the last mode.
Ridge and furrow glazing has been already described?. There are some other varieties; but as they are either well known, or unsuitable for hothouses, they do not require to be particularized.
Specification, &c. August 1811.
See page 23. These eight modes of glazing, and some other modes of less note, may be seen combined in the greenhouse and pit erected here, and frequently referred to.
There remains only to remark on the improvements which have been made in hotbeds and hotwalls.
Various gardeners have endeavoured to economize the stable dung generally used for HOTBEDS, by mixtures of earth, turf, ashes, sawdust, bark, &c. which might at the same time moderate and prolong its heat. For the same purpose, bundles of sticks, empty barrels, broken pots, stones, turf drains, &c. have been introduced, in forming the bed, immediately under the centre of each intended hill or group of plants. Mr. MoPhail is the first who seems to have given these practices a determinate construction, by forming compartments for the earth and plants, and surrounding them by perforated flues of masonry to which linings are from time to time applied'. Attempts have been made to simplify his method by substituting perforated turf-walls or walls of decayed pease sticks or faggots, instead of the flues, &c. Neatness has also been studied, by placing the frames on pillars of brick or stone?, on perforated brick walls, and by sinking the bed of dung in a pit, and covering the linings by boards, &c.3
Laurence in the last edition of his Kalendar (1715) suggests the idea of putting a bottom of wire to the frames of hotbeds, and of covering it with flat tiles, and over these the earth, &c. so as to admit of the whole being lifted, and the dung stirred or renewed at pleasure. He
says he has not seen it done, but merely throws it out as a hint to the ingenious. Nearly a century afterwards Mr. Weeks+ invented his patent forcing-frame, the bottom of which is formed of wood, detached from the frame, and winds up so as to leave free access to the dung, or retain the plants at any required distance from the glass in the day time. This plan promises considerable advantages,
McPhail On the Culture of the Cucumber, &c. 2d edit. London, 1795. • Beattie in Caledonian Hort. Trans. vol. i.
Sanderson, Ibid. vol. ii. and Niel On Scottish Gardens and Orchards. * Hothouse-builder, King's Road, Chelsea. See Repertory of Arts, vol. xiii. p. 81; and The Forcer's Assistant, by Edward Weeks, Chipping Norton, 1814.
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
Mawe's and Macdonald's Dictionaries of Gardening, &c.
spring; by metallic reflectors to concentrate the calorific
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 mixtures), the mechanical effect of compressing air in cast iron boxes or tubes, 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 8, boards placed horizontally and perpendicularly9, oiled paper
! Bath Society's Papers.
As a certain proportion of sulphur, iron, and lime, &c. * Mr. Dalton has estimated that air compressed to half its dimensions has its temperature ele. vated 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 coydensed 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.