286 



VENTILATION. 



under them; and, when slightly heated, 

 it will ascend again through the house. 



Referring, again, to the mode of open- 

 ing and shutting our front ventilators, 

 noticed above, we ought to observe, that 

 any number of the sliding covers can, by 

 a very simple contrivance, be thrown out 

 of gear, and so remain stationary while the 

 others are movable. This range consists 

 of three vineries, any one of which can 

 be left unventilated while the others are 

 open. In consequence of the area air- 

 drain being placed along the front of the 

 house, and occupying 22 inches of space, 

 the vines have, of course, to be planted 

 beyond this area, and their stems brought 

 through apertures formed in the brick- 

 work, and under the plinth, and then up 

 within the house. 



However front air be admitted, it is 

 evident that it should be let in at as low 

 a point as possible, as there is no diffi- 

 culty in getting cold air to descend 

 to the extent required in hothouse 

 arrangements; and that it should be 

 warmed to as near the temperature of 

 the house as possible, is equally clear. 

 But this heating of the air should not be 

 secured at the expense of its purity, nor 

 by lessening the degree of humidity 

 natural to it. When cold air has to 

 pass over highly heated flues, unless 

 humidity be added to it at the same 

 time, it loses much of its real value ; but 

 heated air may be brought over hot-water 

 tanks or gutters, as in the two cases 

 last alluded to, with great advantage. 

 It will readily be understood that aera- 

 tion produced by these means may go on 

 night and day, as the temperature of the 

 house is not affected by it. This, if not a 

 new, is at least a very important feature 

 in hothouse management, and could not be 

 effected by the modes hitherto in use. 



Fig. 382 represents a mode of mecha- 



Fisr 382 nical ventila " 



8 * ' tion very good 



in warm wea- 

 ther, when the 

 external tem- 

 perature is 

 little below 

 that in the 

 house. The 

 front sashes 

 are hung upon 

 pivots at their centres, and are opened and 



shut by means of a long handle with a com- 

 pound joint, reaching from the front to 

 the back passage, or other convenient 

 place. Again, front sashes may be hung 

 by hinging their upper stile to the 

 bottom of the upper wall-plate, and 

 opened and shut by the same means as 

 those above described. Or an iron axle 

 or cylinder may extend the whole length 

 of the house, and each light be attached 

 to it by an iron crank ; and by a lever 

 handle made fast to either end — or, better 

 still, to the middle of the cylinder — the 

 whole may be opened or shut at once. 



The same contrivances may be em- 

 ployed for opening and shutting the top 

 ventilators, which are usually of wood, 

 and, being lighter, are much more easily 

 operated on. 



Where the walls of hothouses are built 

 hollow, a very good mode of aeration 

 may be adopted without the danger of 

 cold draughts of air injuring the plants, 

 or greatly reducing the temperature. 

 This consists in opening holes in the 

 walls, close to the floor, in the inside of 

 the house, and corresponding openings 

 on the outside, and near the top of the 

 walls. The cold air will enter at these 

 top openings, and descend through the 

 vacuities, and enter the house close to 

 the floor. This method we have adopted 

 in the two orchid-houses at Dalkeith, 

 and with the best results. One of the 

 many evils of the former methods of 

 ventilating hothouses was having the 

 front openings too high — generally several 

 feet from the floor — leaving the lower 

 part of the house, where the roots and 

 part of the stems and foliage are, entirely 

 without change of air, excepting the 

 occasional supplies admitted when the 

 door was opened, — a supply entirely 

 inadequate for their health and welfare. 



A very simple and efficient plan of 

 ventilation has been adopted by Mr 

 Fleming in the case of the houses at 

 Trentham, of which figs. 383 and 384 are 

 illustrations. One peculiar advantage of 

 this method is its being simple, and little 

 liable to derangement, — a very important 

 consideration in garden architecture. 



When last at Trentham, we had not 

 time to make a detailed drawing of this 

 mode of ventilation, as there is so much 

 to see and to admire in the improvements 

 that have taken place there of late years. 



