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der the direction of the younger Clusius and of the celebrated Boerhaave'.

BOERHAAVE in designing these houses seems to have been the first to establish a principle for determining the slope of glass, which he develops in his System of Chemistry?, and which are designated in the Amanitates Academicæ, and in the Encyclopédie Méthodique, “ the laws of Boerhaave.” Illustrating the laws of light in its passage through glass, he observes, that gardeners often feel the bad effects of placing the upright sashes of conservatories in such a position as that the sun's rays do not pass through them perpendicularly, and consequently that much of the upper part of the house is deprived of his influence. He recommends erecting the glass windows to an angle of 14 deg. 30 min. in those countries where the elevation of the pole is 52} deg. for reasons easily deduced from astronomy and dialling".

1 See Index Plantarum, &c. and also the preface to Index alter Plantarum quæ in Horto Academico Lugduno-Batavo aluntur conscr. ab H. Boerhauve 1720. The following are the houses alluded to:

Hortus adonidis cum supposito caldario primus.
Hortus adonidis alter magno tepidario hypogeo instructus.
Horti adonidis minores fenestris vitreis et ligneis defensi.
Hortus adonidis maximus fornace calescens.
Pergula hybernaculum præbens variis fornacibus instructum.
Hybernaculum priore calidius.

In the two first of these houses the fire was lighted in a vault; the third had no fire, and the three last were heated by upright German stoves without horizontal flues. This celebrated garden is still visited by the curious. In 1814 it was rather in a state of decay, probably from want of funds, though under the direction of an intelligent old Scotch gardener. It may necessary to remark, for those who are unaccustomed to botanical latin, that Garden of Adonis is a generic term for every description of glass case for preserving or cultivating plants. See a technical arrangement of horticulture in Amænitates Academicæ, tom. iv. p. 211. . Elementa Chemiæ, Lugd. Bat. 1732, tom. i. p. 213. Tom. i. Descriptio Ilorti Upsaliensis.

Volume d' Aratoire et du Jardinage, art. “Serre." 36 Oportet hæc hybernacula, directe meridiei opposita, instruere fenestris e vitro erectis ad angulum 14 gr. 30' usque ad pavimentum, iisque pellucidis, si fieri potest. Postea autem lacunar debet ita fieri, ut a linea horizontali, ducta ab altitudine luminum, a fenestris parietem

be

We find LINNÆUS in 1745 approving of the garden of Leyden in the arrangement of that at Upsal', and stating in his description of the Caldarium, or dry stove, which he erected there in 1740, the advantages of the particular slope which he had fixed on for the glass roof?; no doubt from consulting the laws of Boerhaave, of whose slope for an orangery in latitude 521 he gives a diagram in a plate.

ADANson is the next Continental author of importance who has touched on this subject. . In his “ Familles des Plantespublished in 1763, he has given the first systematic treatise on the theory and practice of constructing hothouses, that probably ever was published. Botanic stoves and greenhouses were the description he had chiefly in view, and these he says ought to be so contrived as to have most sun when the plants are in them. He recommends the use of front glass only; placed upright, or at such an angle as that the sun should be perpendicular to it in November, December, January, and February. The perpendicularity of the glass, he says, protects from the cold occasioned by falling dews. He recommends iron astragals and Bohemian glass in order to obtain the most light possible. “Sloping sashes,” he adds, “whether convex or a part of a circle, and of which they cover each part with straw mats as the sun leaves it, or simply inclined so as the rays of the sun may be perpendicular to them in the beginning of March, are only good for that month and for April.

“ In general,” he concludes, “it will be more advantageous to in

1

posteriorem versus, deorsum declinet angulo pariter 20 gr. 30' in regionibus ubi elevatio poli est 52{. Ratio ex astronomicis et gnomonicis, facilis eruenda hic brevitatis gratia omittitur.- Elementa Chemia, Lugd. Bat. 1732.

Amanitates, tom. I. p. 41. 2 6 Latus australe Caldarii sola fenestrarum junctura constat hunc in modum inclinatis quem declarat delineatio, in fine hujus opusculi sita, quemque hoc majore adnotatione dignum existimavi, quod Caldarium hac inclinatione fenestrarum, sole radios evibrante, duntaxat ab illo, tan tum caloris adquirit, gradum ut thermometrum ad gradus 30 (that of Celsius is here used) sæpe adscendat, quamvis non facile 20 a 25 admittitur superare gradum hortulani vigilantia ; nec infra 15 gr. hyeme facile descendere, antequam focus defectum solis suppleat."--Tom. I.

P. 39.

cline the floor of hothouses to the sun's rays in February, which is the time when the plants of the torrid zone, shut up during five months; suffer the most, than to incline the glass frames.”

Notwithstanding his own opinion, however, he gives rules, tables, and diagrams, for constructing hothouses to suit every possible situation, from the pole to the equator. In some of these the sloping glass forms the hypothenuse of a triangle; in others part of a trapezium, a segment of a circle, or part of a polygon'. The ground plan also varies from a segment of a circle to a parallelogram. Nicholas FacIO DE DOUILLIER2 is the first writer who

appears to have treated the subject of the solar influence in ripening fruits in this country. This author, who was tutor to the Marquis of Tavistock, and a fellow of the Royal Society, published his treatise in 1699: he does not however enter on the subject of hothouses directly, though the greater part of what he states respecting the comparative advantages of perpendicular and sloping walls will equally apply to sloping or perpendicular glass roofs. It appears that this work was at the time it was published rejected by practical men, but it is replete with ingenuity and mathematical demonstration; and, with the faci

1 « Les meilleurs sont ceux qui ont le moins d'inclinaison ; et ceux qui sont tout droits sont préférables, parce k'ils presentent moins de surface au froid dans le tems ou il u plus de force que le soleil, comme en Novembre, Décembre, Janvier, et Février. C'est

pour

cela

que les chassis inclinés, à la façon Hollandoise soit convexes en portion de sfère et dont on recoudre chake partie avec des paillassons à mesure que le soleil les abandone, soit construits en ligne droite, et inclinés, ainsi que le mur sur lekel sont couchés les arbrisseaux à fruits, tels que la vigne, la pêche, &c. qu'on veut avancer, de maniere qu'ils soient perpendiculaires aux raions du soleil au commencement de Mars, ne sont bons que pour ce mois et celui d'Avril, ou le soleil commence à avoir plus de force que les froids des nuits qui diminuent en s'élevant insensiblement au-dessus de la congélation; encore risk t'on en Avril de voir les plantes brú. lées en un moment, ou par le moindre coup de soleil lorsk'on ne les ouvre pas, ou par les froids de 7 à 8 deg. lorsk’on les ouvre trop tôt.See the whole article entitled Manière de conserver vivantes dans des serres les plantes des climats les plus chaudes, tom. i.

. Fruit Walls improved by inclining them to the Horizon; or A Way to build Walls for Fruit Trees, whereby they may receive more Sunshine and Heat than ordinary. By a Member of the Royal Society, London, 1699.

p. 132.

(7) lities which we now possess of protecting sloping walls, and coupled with the information communicated by Dr. Wells', may give rise to real improvements.

LAURENCE”, BRADLEY", LONDON and W18E4, SWITZER5 and others, have noticed the improvement proposed by M. Facio: but MILLER is the first practical gardener who avowedly treated of the subjects both of inclined walls and sloping glass, with a view to their appl cation to horticultural architecture. He mentions the author of “ Fruit Walls inclined, &c.” as having “shown by calculation that there will be a much greater number of the sun's rays fall on a wall inclined to the horizon, than on one perpendicular to it;” and of having "taken the trouble of calculating the different inclinations which such walls should have in the different climates, in order to receive the greatest number of the sun's rays.” Miller, as is justly remarked by the author of the excellent historical introduction to the “ London Fruit Gardener," was too apt to condemn his contemporaries, and does not treat Facio with the respect to which he is justly entitled. He condemns the plan with but little argument: and as he was at that time considered in England as the arbiter olitorum et hortulanorum, and on the continent as omnibus in hac arte palmam præripienso, it will readily be conceived that his ipse dixit would be sufficient to prevent inclined walls from being tried experimentally. As far as I have been able to ascertain, they were only attempted at Belvoir Castle under Facio's directions. There they were unfortunately built on banks of earth, and found accordingly to be damp, thereby'affording Miller a local argument against them, which has been repeated as a funda

1

Essay on Dew, 1814. * Fruit Garden Kalendar, 1718. Introduction, pp. 13 and 22.

s New Improvements in Gardening, art. “Stove:” and in various works by this author from 1700 to 1724. * London Fruit Gardener, chapter on Walls.

Practical Fruit Gardener, art. Wall. 6 Amænitates Academicæ, tom. iv. 213.

mental one by almost every writer who has touched on the subject; from his time to the present day; including the compiler of an able article on horticulture just published in the Edinburgh Encyclopedia'.

In the seventh and eighth editions of Miller's Dictionary (the last published in 1768) the articles STOVE, Sun, GREENHOUSE, and several others, are considerably enlarged by reflections and arguments on the slope of glass roofs; in all probability suggested by Facio, Boerhaave, and what the author had seen during his stay in Holland. Speaking of dry stoves, he says they may either be built with “ upright and sloping glass” or “ with the latter” only“ placed at an angle of 45 degrees, the better to admit the rays of the sun in spring and autumn when the sun declines.” This he says “ has been the general practice;" but he adds, “where I have had the contrivance of stoves of this kind I have always built them after the model of the bark stove (i. e. with upright and sloping glass); because this will the more easily admit the sun at all the different seasons; for in summer when the sun is high, the top glasses will admit the rays to shine almost all over the house, and in winter when the sun is low, the front glasses will admit his rays; whereas when the glasses are laid to any declivity in one direction, the rays of the sun

of the sun will not fall directly thereon above a fortnight in autumn and about the same time in spring 2.”

We are informed under the article Sun, that as the difference between the heat of summer and winter depends on the obliquity of the sun's rays, this should be well considered in the contrivance of stoves, which ought to have their glasses so situated, as to receive the sun's rays in direct lines, during as great a portion of the year as possible; “ for which reason the stoves which have upright glasses in front, and sloping glasses over them, are justly preferred to any at present contrived.”

It is proper to remark here, that forcing houses for grapes and

* Mr.P Niel, Secretary to the Caledonian Horticultural Society.
• Miller's Dict. art. Stove.

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