290 



VENTILATION. 



Fig. 392. 



side wall 2 feet by 10 inches, placed close 

 to the floor, and furnished with box ven- 

 tilators in Atkinson's manner. In the 

 other case, the same kind of ventilators 

 are built in the front wall. The cold air 

 admitted by them has to pass up the side 

 of a hot-water tank, and becomes thereby 

 warmed before coming in contact with 

 the plants. The back wall is built hol- 

 low, and openings 4 inches square are 

 made on the outside, near the top, by 

 which cold air enters, and, descending the 

 wall, enters the house by similar openings 

 close to the floor. This latter ventilation 

 is left open day and night. 



Ventilators in the back 

 walls of houses may also be 

 opened and shut very con- 

 veniently, even when at 

 a considerable height, by 

 hanging them at top with 

 hinges, or by pivots at their 

 centres, and attaching them 

 to a long rod of iron, per- 

 forated with holes at the 

 lower end, to fix on pins or 

 iron studs driven into the 

 wall. Fig. 392 will show 

 the principle. 

 And front ones, if hung so 

 as to open inwards, may be opened and 

 shut without treading upon the border, by 

 attaching a line to their lower edge, to be 

 brought over a small brass pulley, fixed 

 to the inner edge of the wall-plate, car- 

 ried upwards under the roof, and made 

 to pass over another pulley, fixed to the 

 under side of the top-rail of the bottom 

 sash, leaving a sufficient length of line 

 to hang down to be within the conve- 

 nient reach of a person standing in the 

 footpath. A slight pull of this line 

 will open the lid of the ventilator to any 

 extent ; and if the end of the line be 

 furnished with a small iron or brass eye, 

 it may be fastened to hooks in the back 

 wall, so as to give sufficient head-room 

 over the passage. To secure the shutting 

 of the ventilator, it should be loaded at 

 the bottom by having a plate of lead or 

 iron screwed to its outer side, sufficiently 

 weighty not only to cause it to shut, but 

 to keep it so. 



A very ingenious mode of ventilation 

 is described in the " Gardeners' Journal," 

 as practised at Beau-Manor Park. It is 

 to the following effect : — " Along the top 



of the back wall of the houses, below the 

 centre of each light, there is a square 

 cast-iron frame built into the wall. In 

 this frame is placed a ventilator of thin 

 iron, having a wire spring and ball 

 attached to its lower end. Beneath the 

 pits in the centre of the houses are a 

 number of air-drains, brought into the 

 interior of the house from the sheds con- 

 taining the fires and boilers. The air 

 coming through these drains causes a 

 circulation of air within the houses, and 

 this, acting upon the ventilators, (which 

 are nicely balanced by means of the ball,) 

 causes them to open for the escape of 

 the heated air ; but the moment that the 

 cold air rushes down the shaft towards 

 the ventilator, it immediately closes — 

 thus preventing the admission of cold 

 air. All the ventilators do not open at 

 the same time, but, as it were, in rota- 

 tion." Of course, the operation of these 

 ventilators goes on day and night, and 

 therefore that perpetual change of air so 

 necessary to plants must be also perpetu- 

 ally going on. The mechanical contrivance 

 is so simple and devoid of complication, 

 that a diagram of it would be superfluous. 



Another useful mode of ventilating 

 pits is described by an anonymous writer 

 in the " Gardeners' Magazine," and is 

 upon the principle of opening the roof- 

 lights all at once to any extent ; and also, 

 instead of elevating them at the back, 

 as is usually done, they are elevated at 

 the sides, which causes a more equal 

 degree of ventilation — a practice long in 

 use, but, so far as we know, effected only 

 by lifting each sash individually, and 

 propping them up with a flower-pot or 

 wedge-shaped piece of timber. In this 

 case mechanical power is applied, which 

 performs the operation quicker and with 

 more security. " For this purpose," he 

 says, " I would have a hook {I, fig. 393) 



Fig. 393. 



fixed to the middle of both sides of the 

 frame, and holes in the flat part of the 

 iron rod m, to catch on these — the ends 

 of the rod having a series of holes to 

 graduate the height — and, when drawn 



