A. As carbon has a very great affinity for oxygen, therefore, whenever they are exposed to heat, they _combine_, and form carbonic acid gas (or what is vulgarly called fixed air). Q. _Is CARBONIC ACID GAS wholesome?_ A. No; it is quite _fatal to animal life_; and whenever it is inhaled, it acts like a narcotic poison, (producing drowsiness which ends in death). Q. _Why is a CROWDED ROOM UNWHOLESOME?_ A. Because the oxygen of the air is either _absorbed by the lungs_, or substituted for _carbonic acid gas_, which is a noxious poison. Q. _Mention the historical circumstances, so well known in connection with the "BLACK HOLE of CALCUTTA."_ A. In the reign of George II, the Raja (or Prince) of Bengal[12] marched suddenly to Calcutta to drive the English from the country; as the attack was unexpected, the English were obliged to submit, and 146 persons were taken prisoners. [12] The Sur Raja, at Dowlat; a young man of violent passions, who had but just succeeded to the throne. A. D. 1756. Q. _What became of these prisoners?_ A. They were driven into a place about 18 feet square, and 15 or 16 feet in height, with only two small grated windows. 123 of the prisoners died in one night; and (of the 23 who survived) the larger portion died of putrid fevers, after they were liberated in the morning. Q. _Why were 123 persons SUFFOCATED in a few hours, from confinement in this close hot PRISON-hole?_ A. Because the _oxygen of the air_ was soon consumed by so many lungs, and its place supplied by _carbonic acid_ exhaled by the hot breath. Q. _Why do persons in a crowded CHURCH feel DROWSY?_ A. 1st--Because the crowded congregation _inhale a large portion of the oxygen of the air_, which alone can sustain vitality and healthy action: and 2ndly--The air of the church is impregnated with carbonic acid gas, which (being a strong narcotic) produces drowsiness in those who inhale it. Q. _Why did the captives in the BLACK HOLE die SLEEPING?_ A. 1st--Because the _absence of oxygen_ quickly affects the vital functions, depresses the nervous energies, and produces a lassitude which ends in death: and 2ndly--The _carbonic acid gas_ inhaled by the captives (being a narcotic poison) would also produce _drowsiness and death_. Q. _Why do PERSONS, who are so much in the OPEN AIR, enjoy the best HEALTH?_ A. Because the air they inhale is _much more pure_. Q. _Why is COUNTRY AIR more PURE than the air in CITIES?_ A. 1st--Because there are fewer inhabitants to vitiate the air: 2ndly--There are more trees to restore the equilibrium of the vitiated air: and 3rdly--The free circulation of air keeps it pure and wholesome (in the same way as running streams are pure and wholesome, while stagnant waters are the contrary). Q. _Why does the SCANTINESS of a country POPULATION render the COUNTRY AIR more PURE?_