292 



VENTILATION. 



was raised to within a yard of its full 

 height, apertures were formed in the man- 

 ner of a common chimney or fire-place, 

 18 inches wide and 2 feet high, from which 

 a small vent was carried through the 

 coping. On the top was fixed a horizon- 

 tal tube, 3 inches square and 2 feet long, 

 with a centre pipe fixed in the vent. The 

 aperture or chimney was filled in front 

 with two movable panels or boards, hung 

 in the manner of common sashes, the one 

 to move up and the other down, for the 

 admission of air through the tube at the 

 top — thus diverting or breaking a strong 

 current, which might be prejudicial to 

 the grapes. Ventilators in front, at the 

 distance of 6 or 8 feet from one another, 

 may be made thus : — Pierce a hole, an inch 

 in diameter, through the bottom rail of 

 the under sash, if the house has no up- 

 right glass ; or through the upper rail of 

 the upright sash, if it have one. In this 

 hole insert a tin tube to fit, having a 

 funnel mouth outwards, and a fine rose, 

 like that of a watering-pot, to fit to it 

 inside. The tube should be made in 

 lengths of 2 feet each, that the air may be 

 either diffused as it enters through the 

 front, or be carried to the centre of the 

 house, or further if thought necessary. 

 When not in use, it ought to be stopped 

 with a cork or plug. When a full stream 

 is wished, the rose need not be put on; 

 but it should if the air is keen. In order 

 the better to collect the air, the funnel 

 should be pretty large — that is, about 7 

 or 8 inches in diameter. With these, and 

 with the ventilators at or near the top of 

 the back wall, as mentioned above, any 

 hothouse may be safely aired or venti- 

 lated even in the severest weather ; and 

 also when it may be improper to open 

 the glasses, as during rain." This appears 

 to have been the earliest idea of venti- 

 lating otherwise than by movable sashes. 



The annexed cut, fig. 397, exhibits a 

 mode of ventilating the roofs of large 

 houses, which has been most successfully 

 employed by Mr Turner of Dublin in the 

 case of the large conservatory at the gar- 

 dens of the Royal Botanic Society in the 

 Regent's Park. As will be seen by a glance 

 at our figure, the roof sashes are furnished, 

 on the under sides of their side rails, 

 with brass castors, which run on the rafters, 

 and are suspended by a flexible chain, 

 made to pass over and under a cylinder 



placed immediately under the ridge. This 

 chain is thence brought down under the 



Fig. 397. 



roof, and passed over a pulley at the 

 springing of the roof, and from thence to 

 the bottom of the supporting columns, 

 where it is wound up by a simple cog- 

 wheel, which, when acted upon, draws up 

 the sashes of each side of the ridge, more 

 or less, or to their full extent, according 

 to the will of the operator. From the 

 construction of the roof in this conserva- 

 tory, it became necessary that top venti- 

 lation should be effected from within ; 

 and probably few better modes of accom- 

 plishing this could have been adopted. 



Week's improved mode of ventilating con- 

 sists of a sloping roof sash, which may be 

 of any size, and applicable to any sloping- 

 roofed hothouse. It is worked upon the 

 principle of a parallel ruler placed edge- 

 ways. It is thus described by Dr Lind- 

 ley, who says " it has all the appearance 

 of being a contrivance of much practical 

 value. Let the rafter be represented by 

 the lower half of such a ruler, and the 

 sash itself by the upper half; it is evident 

 that if any movement of elevation is com- 

 municated to the sash, the immediate 

 result will be the withdrawal of the sash 

 from the top or wall plate, and the open- 

 ing of a space all round, while at the 

 same time the sash itself remains pretty 

 nearly over its own bed. The elevating 

 and depressing movement is produced by 

 a crank, a wheel, and a horizontal bar, so 

 that any number of sashes can be elevated 

 or depressed at the same instant." 



