MANDAI, OF NATURE STUDY. 79 



•wide under the entire lower sash; such an arrange- 

 ment will prevent rain or snow from blowing into 

 the room and will at the same time permit fresh air 

 to enter between the sashes. For sitting rooms, 

 the old fashioned fire place, or open grate, is the 

 best means of ventilation. What makes the fire 

 roar in open fire places? And the flames to wal- 

 low up the chimney? (Ascending current of air 

 from the room.) Which is better ventilation, a soft- 

 coal burner with an open hearth or a hard-coal base- 

 burner ? Why ? Why does the base-burner cause 

 head-ache so often conplained of in warm rooms ? 

 (Because the draft through the fire is not strong 

 enough to carry off the bad air of the room and 

 also because carbon monoxide leaks out of the 

 stove and diffuses itself throughout the room, 

 thus rendering the air extremly poisonous and 

 dangerous.) 



Enumerate instances of persons poisoned by escap- 

 ing gas from a base-burner. Tell the story of the 

 Black Hole of Calcutta, where one hundred and forty- 

 six persons were shut up for the night and only twen- 

 ty-three were found alive at dawn of day. Also, one 

 stormy night, one hundred and fifty persons were 

 crowded into the cabin of a ship and only eighty 

 came out alive. What makes children listless and 

 drowsy in a warm, close school room? Why do 



