258 



MACHINERY IX CONNECTION VVITII AIR. 



the thermometer frequently indicates twenty degrees dif- 

 ference in the heat above and at the floor, the lower 

 stratum of air resting like a cold lake about the feet, 

 while the head is heated unduly. 



When the draught of the chimney-fire is not strong, 

 the smoke may, however, escape through the ventilating 

 register into the room. To avoid this difficulty, it is best 

 to provide separate air-flues in the walls when the house 

 is built, for effecting perfect ventilation. In rooms strong- 

 ly heated by fires, the fresh air should be admitted near 

 the ceiling, producing descending 

 currents, and effecting a complete 

 circulation in the air of the room. 

 But in sleeping apartments, and in 

 closets, not heated artificially, and 

 where the descending currents will 

 not take place, the fresh air should 

 Mode of Ventilating Garrets. \fQ admitted througli a rcgistcr or 

 small rolling blind near the floor, and discharged near the 

 ceiling into an air-flue. 



The excessive warmth of garrets in midsummer may 



Fig. 285. 



Fig. 2S4. 



Mode of Ventilating half-story Bed- 

 rooms. 



Gnffil^i's VentUalor. 



be avoided by placing a ventilator at the highest part, 



