Зображення сторінки
PDF
ePub

A

Fig. 12 shows the manner in which a tinned hoop may be bent and applied to the underside of a solid iron astragal; some of which I have used in ridge and furrow glazing. Where the lap used is such as to throw the water to the astragal, and the roof is flat, any of these forms may be found useful; but I may here repeat, that wherever an outer curtain is used condensation will very rarely take place.

The bearing bars of sashes, or those on which long astragals are caused to rest, between the top and bottom rails, and with which they are kept steady, in regard to breadth, ought to be so formed and placed as to effect these objects without interrupting the course of the water of condensation in its progress down the mouldings of the astragals.

Fig. 13, PL. X. is a very good form for this purpose; Fig. 14 is the form for which Mr. Jorden has taken out a patent; but Fig. 15 is by much the best mode, as it not only strengthens the astragals more than any other, but can never in any way interrupt the water of condensation. In all cases it will be an improvement not to fix these bars directly across the sash, but obliquely, so as the water which condenses on them may be thrown to one side, and so carried off with that on the astragals, rails, or sashes. This last mode is particularly suitable for solid iron astragals. It is due to Messrs. Timmins and Jorden to state, that they have paid more attention to water escape bars than any other hothouse builders.

Notwithstanding the permanency and lightness of metallic rafters and sashes, various cases may occur where timber will have the preference,—as for example where the ground on which the building is to be erected is held for a limited term, and where from prospective arrangements durability is less an object than present use. These cases may occur combined in the wants of a nurseryman or public gardener; and where there exists no such reason, the experience of the gardener, or prejudice of some favourite menial, (and most country gentlemen, indeed all of us, are more led by some obscure localized dependant than by reason and common sense,) may lead to the same

conclusions. To promote therefore the durability of timber houses, in addition to the remarks already submitted as to the use of tar, &c. let them be formed on as light a construction as possible, and, when wide, well supported by props or pillars; the joints not held together by tenon pins, but by tenon wedges, and all the joints set, not in glue, but in white lead'.

Glazing. Formerly the worst description of crown glass was used in hothouses; but if, as Bouguer has shown, one fortieth part of the light which falls perpendicularly on the clearest crystal is reflected, or does not pass through it, green glass must at least reflect or exclude one half. Economy in glass is therefore no œconomy, and produces effects really as disagreeable to the eye as injurious to vegetation.

The air which enters between the laps of the panes in hothouses first suggested the idea of closing these with putty, or with a lead lap similar to what is used in lattice windows. This being found to prevent the condensed dews from escaping outside the glass, gave rise at first to closing the lap partially with putty, and subsequently to different modes of cutting and disposing the panes. The principal modes are as follow.

Common hothouse glazing. Fig. 5, PL. IX. shows the common form of pane. If the lap or projection is unputtied, its breadth may be from one quarter to three quarters of an inch; when wholly puttied, it need not project above a quarter of an inch; and when a space one inch long is left open in the centre, the projection may be half an inch. In these cases, the glass is of course placed obliquely to the plane of the rabbet which contains it.

Fragment glazing. Fig. 6 represents a mode of glazing with fragments of glass, which are generally lost or but of little use to the glass

This, as well as the use of tar, is practised by Mr. Pilbrough, carpenter and builder, New Milman-Street, Foundling Hospital, whom from experience I can safely recommend as an improved wooden hothouse builder.

Traité d'Optique; and Dr. Young's Lectures, 35 and 39.

cutters. It is chiefly adopted by nurserymen and market gardeners for the sake of œconomy, 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 me 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

[blocks in formation]

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.

[blocks in formation]

* 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 œconomize 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. McPhail 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 stone2, 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.

3 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.

« НазадПродовжити »