278 METHODS OF VENTILATION. 



whole house may be aired in the space of one minute ; or as 

 many houses as may be in the range. This is effected by a rod 

 passing along the whole length of the house. A pulley is fixed 

 immediately above each ventilator, and another placed opposite 

 it upon the rod, as shown in Fig. 51. A piece of chain or cord 

 is attached to the ventilator at one end ; and passing over the 

 pulley, as shown at a, Fig. 52, is then fixed to the pulley placed 

 opposite it upon the rod. A larger wheel, or pulley, is fixed at 

 one end of the rod, (,) to which is attached a chain, connected 

 with a crank, situated within the reach of a person standing on 

 the floor. This crank is fixed on the back wall, as seen at c, 

 Fig. 52. 



From the foregoing cuts and description it will be perceived 

 that, by giving the crank (d) a few turns, the whole of the ven- 

 tilators will be opened. The crank is provided with a racket, so 

 that they may be opened to any distance, from half an inch to 

 the full height. 



The ventilators in the front wall may be opened and shut by 

 the same method, and may be, for convenience, brought from the 

 outside. Any length of house, or any number of houses, may 

 be ventilated at once by this method, providing the apertures 

 are in a straight line; their perpendicular distance from the 

 horizontal shaft makes no difference in their facility of working. 

 The pulley cords of the higher ones only require to be length- 

 ened according to the distance, the diameter of the wheel on 

 which the cord turns being equal all along the shaft. 



6. Figures 54 and 55 represent a method of ventilating 

 span-roofed houses. It is employed in the houses at Frogmore, 



Fig. 54. 



