VENTILATION. 



295 



cipally adapted to dwelling-houses, but 

 which might be applied, we think, with 

 much advantage to hothouses also, may- 

 be noticed Sheringham's ventilator, Dr 

 Arnot's ventilating valve, and Moor's 

 patent lever ventilator. The first of 

 these is so arranged that any requisite 

 quantity of air may be admitted without 

 the slightest draught being felt ; and as 

 the apparatus is placed in the external 

 wall, its action is not impeded when the 

 house is closed for the evening, at which 

 time a constant supply of air is most 

 required. Dr Arnot's ventilating valve 

 is too well known to require any remark 

 from us, farther than that it, as well as 

 the last, may be built in the front 

 parapet, and also in the back walls of 

 lean-to houses, with great advantage. 



Moor's patent lever ventilator is simple 

 and effective, and consists of louvres of 

 glass fitted into brass frames. Its action 

 is produced by a line, which, on being 

 pulled, opens the louvres, and when 

 loosed, again closes them with the 

 greatest nicety; or they may be kept 

 at any degree of elevation, according 

 to the amount of air required. To 

 adapt them to hothouse ventilation, the 

 louvres should be connected at their 

 centres with a metallic rod, having a 

 curved arm to each louvre ; so that, 

 when the upright rod is elevated by 

 means of a spiral screw near its bottom, 

 the louvres will be thrown outwards to 

 any extent not exceeding half their own 

 square, or to any angle under that, and 

 kept in that position until the upright 

 rod is depressed by a counter motion 

 of the spiral screw, when the whole will 

 shut down quite air-tight. 



Such a contrivance could be attached 

 to either roof or upright sashes, and also 

 to houses already in existence, by taking 

 out every alternate sash, and substituting 

 louvres instead, of a size say 12 inches in 

 breadth, and of a length equal to the 

 space between the rafters. Or, in the 

 case of a new erection, the whole glass 

 thereof might be put in on the louvre 

 principle, and by a very simple appli- 

 cation of machinery the whole roof 

 might be moved at once, and the per- 

 pendicular sides by a separate move- 

 ment. 



General remarks on ventilation. — A series 

 of very excellent practical papers on ven- 



tilation and heating, by Mr Glendinning 

 of the Chiswick Nursery, has been pub- 

 lished in the columns of " The Gardeners' 

 Chronicle." This excellent cultivator 

 very properly begins his remarks on large 

 houses, which the remission of the duty 

 on glass is likely to multiply, as well as 

 magnify. Small houses are easily ma- 

 naged in this respect, particularly those 

 constructed of wood, and glazed with 

 small glass. With those of great magni- 

 tude, of metallic construction, and glazed 

 with large sheets of glass, the case is very 

 different. According to the present de- 

 fective mode of ventilation, plants seldom 

 succeed so well in such houses as in those 

 of more humble pretensions. The bad 

 effects of such houses are soonest mani- 

 fested, as Mr Glendinning very justly 

 remarks, "in houses constructed of me- 

 tallic roofs, and glazed with sheet-glass, 

 thus rendering what is considered elegant 

 and beautiful in these ornamental struc- 

 tures fatal in the application ; as vegeta- 

 tion thrives ten times more luxuriantly 

 under the huge wooden beams and rafters, 

 with green glass and leaden laps. Shad- 

 ing of different kinds has been extensively 

 adopted to counteract the scorching in- 

 fluences of a warm sun ; but this, at best, 

 is a nuisance ; and in some cases it is 

 impossible to remove it with sufficient 

 ease and rapidity to reap the advantages 

 resulting from lightly constructed edifices 

 with clear and spotless glass. Take, for 

 example, a conservatory similarly built to 

 the large building in the Horticultural 

 Society's Garden at Chiswick, and it will 

 be found, in all such erections, utterly im- 

 possible to produce or maintain luxuriant 

 foliation in a general collection of plants, 

 even although considerable command 

 may be had in blinding the sun's rays. 

 The spring leaves being so excessively 

 tender, with every care they are almost 

 sure to get scorched. Plants growing in 

 tropical countries do not suffer in this 

 way, because the. heat of the sun, al- 

 though great, is not increased by artificial 

 means, as in glass-houses, where the ten- 

 sion of the atmosphere becomes immense ; 

 the young juicy foliage is in consequence 

 compelled to part with its moisture, and 

 it withers in an hour. The admission of 

 air to lower the temperature, or rather to 

 prevent the temperature from rising so 

 very rapidly, is a point too often over- 



