5G 



GENERAL FORMATION, &c., OF GARDENS. 



position. On the end of each rod is fixed 

 by a key a pulley c, about 12 inches 

 diameter, which corresponds with a 

 pulley, d, fixed on an axle, and moving in 

 a cast-metal case which is fixed into the 

 wall about 3 feet from the floor. Around 

 those two pulleys, and attached to each, 

 is a neat light chain e ; when the under 

 pulley is moved round, the upper one also 

 moves, and either opens or shuts every 

 alternate top ventilator simultaneously. 



The under pulley is moved by a brass 

 nob being fixed into one of the arms of 

 the pulley, and works round a circular 

 slit made in the outside plate of the case, 

 as seen in No. 1. 



When the ventilators are heavy, and a 

 long range is wanted to be moved, a 

 small spin- wheel, about 10 inches dia- 

 meter, may be fixed on the same axle as the 

 under pulley, and in the corner of the 

 case is placed an axle, with small pinion, 

 about 3 inches diameter, j \ this pinion is 

 moved by a small organ handle, and when 

 turned round it moves the wheel and 

 pulley with a power of nearly four to one 

 — consequently the ventilator sashes are 

 shut and opened with great ease. 



The axles work in bushes cast on the 

 front and back plate of an iron box built 

 into the recess of the wall, which recess 

 extends from the case to the top of the 

 greenhouse, to allow room for the double 

 chain of the two ventilators to run freely 

 up and down. The great advantages of 

 this ventilation are the simplicity of its 

 movement, and its preventing snow or 

 rain from being blown into the house, 

 while, at the same time, all the ventila- 

 tors may be kept open. 



/ / are the astragals of roof ; g g is the 

 bottom of the lantern frame which forms 

 the ventilators ; h h roof of lanthorn, of 

 which the top and sides are glazed. 



The whole of the roofs and gables are 

 fixtures, with a view to prevent the break- 

 age of the glass, which is 21 oz. to the 

 foot, and in pieces 3 feet in length by 12 

 inches in breadth. The intention of ven- 

 tilating by the sides instead of at the top 

 of the lantern part of the ridge is, that 

 air may be admitted during rain or snow. 

 As both sides of the ventilation are acted 

 upon by separate movements, one side 

 may be opened while the other is shut, 

 or both may be opened at the same time. 

 Every alternate panel is a fixture, but 



the opening one on one side is placed 

 opposite to the fixed one on the other. 

 The whole of the machinery is placed 

 in a recess in the back wall, and cover- 

 ed with a facing of wood to keep the 

 wheels and chains dry ; the axle of the 

 pinion j projecting 2 inches over the 

 facing, so that the handle or key which 

 moves the wheels may be applied with 

 greater facility. 



Fig. 31 shows a different mode of ven- 

 tilation, which is applied to all the other 

 houses. Instead of every alternate sash 



Fig. 31. 



n 



J 



or panel being made to move outwards, 

 as in the last example, here they move 

 longitudinally into a groove, provided for 

 the purpose, in the top and bottom rails 

 of the upright part of the lantern, and 

 are acted upon by a small metallic chain 

 connecting all the movable panels on 

 each side together. These chains are 

 made to pass alternately over and under 

 small pulleys, bbbb, and the motive power 

 is given by turning the crank handle a 

 in the right hand direction, when it acts 

 on a rack and pinion c, which pushes for- 

 ward every alternate panel, from half-an- 

 inch opening to its full extent; and, by re- 

 versing the movement of the same handle, 

 they are drawn back again by the same 



