VENTILATING 



135 



Fig. 76. Ventilators (a and b) operated by means of 

 rods with universal joints attached to posts and 

 rafters. No extra columns are necessary. 



usually used and the hand wheel placed at a 

 convenient position for the operator. When 

 there are no benches along the sides a com- 

 pact device is advisable in order to take up as 

 little room as possible (Fig. 78). 



