MANUAL 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 
