It is one of the elementary bodies, and is very abundant throughout nature. It abounds mostly in vegetable substances, but is also contained in animal bodies, and in minerals. The form in which it is most familiar to us is that of _charcoal_, which is carbon almost pure.
19. _What is meant by an elementary body?_
An elementary body is one of those substances in which chemistry is unable to discover more than one constituent. For instance, the chemist finds that water is composed of _oxygen_ and _hydrogen_. Water is therefore a _compound_ body. But _carbon_ consists of _carbon only_, and therefore it is called a simple, or elementary body.
[Verse: "Where no wood is, there the fire goeth out: so where there is no tale-bearer, the strife ceaseth."--PROVERBS XXVI.]
20. _Why is it dangerous to burn charcoal in rooms?_
Because, being composed of _carbon_ that is nearly pure, its combustion gives off a large amount of _carbonic acid gas_.
21. _What 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 the 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 own 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.
Oxygen is one of the most widely diffused of the elementary substances. It is a gaseous body.