THE BEA8O3* TVHY. 3] 



"Where DO wood is, there the fire goeth out : so where there is no tale- 

 the strife ceaseth." FEOVERBS xsvi. 



20. Why is it dangerous to burn charcoal in rooms ? 

 Because, being composed of carbon that is nearly pure, its com- 

 bustion gives off a large amount of carbonic acid gas. 



21. Wliat is the effect of carbonic acid gas upon the human 

 system ? 



It induces drowsiness and stupor, which, if not relieved by 

 ventilation, would speedily cause death. 



22. What is the reason that people feel drowsy in crowded 

 rooms ? 



Because the large amount of carbonic acid gas given off with tho 

 breaths of the people, makes the air poisonous and oppressive. 



23. What other causes of drowsiness are there ? 



The candles, gas, or fires that may be burning in the rooms where 

 people are assembled. Three candles produce as much carbonic 

 acid gas as one human being ; and it is probable that one gas-light 

 produces as much carbonic acid gas as two persons. 



24. Have people ever been poisoned by their oion breaths ? 

 In the reign of George the Second, the Rajah of Bengal took 



some English prisoners in Calcutta, and put 146 of them into a 

 place which was called the " Black Hole." This place was only 18 

 feet square by 16 feet high, and ventilation was provided for only 

 by two small grated windows. One hundred and twenty-three of 

 the prisoners died in the night, and most of the survivors were 

 afterwards carried off by putrid fevers. Many other instances have 

 occurred, but this one is the most remarkable. 



- CHAPTER III. 



25. What is oxygen ? 



Oxygen is one of the most widely diffused of the elementary sub- 

 stances. It is a gaseous body. 



26. Wliy do persons ivho are walking, or riding upon horse* 

 back feel warmer than when they are sitting still ? 



