Ventilation and Heating. 119 



ought to be dry, well lighted, and well ventilated. But 

 since many of them are dark and ill ventilated, especial 

 care should be taken to keep them dry. Fruit and vege- 

 tables should not be allowed to decay in the cellar. On 

 entering many houses one can at once detect the smell 

 of decaying potatoes and other vegetables. Such material 

 should be promptly removed. The best time to ventilate 

 a cellar is at night, for if the cellar windows are opened 

 in the day time, the entering air will deposit moisture, 

 making the cellar more damp instead of dryer. 



Summary. i. Lung diseases usually accompany close confinement, 

 but are rare with those living in the open air. 



2. Air in rooms needs constant renewal. 



3. Grates are good ventilators, but not economical heaters. 



4. Stoves are economical heaters, but poor ventilators. Both grates 

 and stoves heat very unevenly. 



5. All crowded rooms, as schoolrooms and churches, need special 

 inlets for fresh air and outlets for foul air. 



6. The most common means of withdrawing the air is by foul-air 

 shafts. Heat is the force relied on, but the removal of foul air is usually 

 inadequate, on account of the slowness of the current or the narrowness 

 of the outlet, or both combined. 



7. Fans are much more certain to be effectual. 



8. Steam and hot water may heat directly (by radiation) or indirectly 

 (placed in flues). It is best to combine direct and indirect heating. 



Questions. i. How can we renew the air of a room without having 

 unpleasant drafts? 



2. Should bedroom windows be open at night? Is night air bad? 



3. What dangers in the use of hard coal ? 



4. Should there be a damper in the smoke-pipe of a hard coal stove ? 



5. What do miners mean by " choke damp ?1 ? 



6. Compare stove and furnace heating. 



7. Compare heating by steam and by hot water. 



8. Read about the " Black Hole of Calcutta. 11 



