VENTILATION. 



tural Society's Garden ventilated by that 

 gentleman. Our 

 F,g - 3(3L section and de- 



scription are 

 taken from the 

 Transactions of 

 that Society. 

 The principle, 

 however, to be 

 understood, re- 

 quires that we 

 should state that 

 the roofs are 

 fixed, and may 

 either be all in one piece, or divided by 

 rafters into many sashes, as in ordinary 

 houses. The object was to provide ample 

 ventilation, without the danger of breaking 

 the glass by pulling the sashes up and 

 down ; and also 

 Fig. 362. tQ ventilate cur _ 



vilinear houses, 

 as in our dia- 

 gram, fig. 362, or 

 straight - roofed 

 houses in the 

 usual way, as 

 fig. 361. This 

 Mr Atkin- 

 favourite 

 form — the sashes 

 being fixed, and 

 i * 1 the usual front 



or perpendicular sashes entirely dis- 

 pensed with, the roof resting on the 

 front parapet wall a, and at back upon 

 the face of the back wall at b. " In 

 the front wall are built a number of 

 wooden frames, into which shutters, 

 opening externally on hinges, are accu- 

 rately fitted, c. In the back wall, within 

 the house, and next the glass at top, are 

 also fitted a corresponding number of 

 wooden frames d, furnished with a wooden 

 slider, running up and down by means of 

 pulleys with cords and weights, after the 

 manner of a window sash. These sliders 

 are interposed between a hollow in the 

 wall /, which communicates with the ex- 

 ternal air in front, above the glass roof of 

 the house g. When it is wished that no 

 air be admitted, the front shutters and 

 back sliders are closed ; and in proportion 

 as it is desired to ventilate the house, they 

 are opened to a greater or less degree. 

 By these means a current of air is main- 

 tained from front to back ; and as fast as 



was 

 son's 



the admitted air becomes heated and 

 rises in the house, it escapes through the 

 ventilators at the top of the back wall. 

 When it is expedient to admit fresh air 

 without loss of much heat, the front 

 ventilators alone are opened. The venti- 

 lation of the houses being thus effected 

 with facility and accuracy, renders the 

 moving of the lights for that purpose 

 unnecessary. By aid of these ventilators, 

 the temperature of iron houses is capable 

 of being lowered in the hottest days of 

 summer to a degree even inferior to that of 

 the external air." To this latter opinion 

 we, however, by no means subscribe ; nor 

 do we think that metallic houses can be 

 reduced, in very hot weather, to so low a 

 temperature by any means of ventilation 

 at present in use. 



A glance at our diagram will show the 

 extent of ventilation effected by this, as 

 well as by all the other modes in houses 

 of the ordinary construction, namely, the 

 space between the dotted line and inner 

 surface of the roof, leaving almost half of 

 the internal space unprovided for — that is, 

 the triangle formed by the dotted line, 

 back wall, and floor. To displace the 

 air which must occupy this space, and 

 which, from its position, is the coldest and 

 most impure in the house — fresh supplies, 

 and consequently motion, must be ob- 

 tained by an opening at h, or by several 

 in the floor, as at i h I, — the former by 

 perforating the back wall, and the latter 

 by bringing an 



Fig. 363. 



"Transactions of the 

 ciety." The object 



air-drain under the 

 ground level, with 

 openings in the 

 floor to admit the 

 air into the house. 



The mechanical 

 contrivances em- 

 ployed in ventilat- 

 ing hothouses are 

 various ; of these 

 the self-acting ven- 

 tilators are the 

 most ingenious. 

 Fig. 363 represents 

 one of this kind 

 invented by John 

 Williams, Esq. of 

 Pitmaston, and 

 described in the 

 Horticultural So- 

 in this, as in all 



