Q. _Why is HOT TEA, &c. cooled more rapidly by BLOWING it?_

A. Because the heated air is _blown more rapidly away_; in consequence of which, _cold air more rapidly succeeds_ to _absorb heat_ from the surface of the tea or broth.

Q. _If a shutter be closed in the day-time, the stream of light (piercing through the crevice) seems in CONSTANT AGITATION. WHY is this?_

A. The air (in the sun-beam piercing through the shutter-crevice) is _more heated_, than _that in its neighbourhood_; the convective current, therefore, is _distinctly seen_, where little motes and particles of dust are _thrown into agitation_ by the _violence_ of the current.

Q. _Why is the GALLERY of a CHURCH or theatre HOTTER than the AISLE or pit?_

A. The hot air ascends from the _bottom_ to the _top of the room_, and cold air (from the doors and windows) flies to the _bottom_ to supply its place.

Q. _Why does a CROWDED ROOM produce HEAD-ACHE?_

A. Because we breathe air _vitiated by the crowd_.

Q. _How does a CROWD VITIATE the AIR of a ROOM?_

A. Whenever we breathe, the elements of the air are _separated_ in the lungs, _some of the oxygen is absorbed by the blood_, and some of it is converted into _carbonic acid gas_, and exhaled with the nitrogen.

Q. _Is ALL the NITROGEN REJECTED by the lungs?_

A. Yes; all the nitrogen of the air is always exhaled.

Q. _What is CARBONIC ACID GAS?_

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 subst.i.tuted for _carbonic acid gas_, which is a noxious poison.

Q. _Mention the historical circ.u.mstances, 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 pa.s.sions, 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 la.s.situde 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?_

A. Because the fewer the inhabitants, _the less carbonic acid will be exhaled_; and thus country people will inhale _pure oxygen_, instead of air _impregnated with the narcotic poison_, called carbonic acid gas.

Q. _Why do TREES and FLOWERS help to make country AIR WHOLESOME?_

A. Because trees and flowers _absorb the carbonic acid_ generated by the lungs of animals, putrid substances, and other noxious exhalations.