THE SCIENTIFIC KNOWLEDGE OF THINGS FAMILIAR.

Auckland Examiner, Volume 1, Issue 1, 11 December 1856, Page 4

THE SCIENTIFIC KNOWLEDGE OF THINGS FAMILIAR.

Q What is Heat ? A. The sensation of warmth. Q. How is the sensation produced ? A. When we touch a substance of higher temperature than ourselves, a subtle invisible stream flows from the hotter substance, and produces on our nerves the sensation of warmth. Q. What is that “ subtle invisible steam” called, which flows thus from one body to another ? A. Cal6ric. Calbric, therefore, is the agent which produces the sensation of warmth; but Heat is the sensation itself, produced by the influx of Caloric. Q. What are the four principal sources of heat ? A. I.—The Sun. 2.—Electricity. 3. —Chemical Action ; and 4.—Mechanical Action. Q. What are the principal effects of heat ? A. Expansion, Liquefaction, Vaporization, and Ingition. Q. What is the principal source of Heat ?• A. The Sun. Q. Why do burning glasses set fire to substance submitted to their power ? A. Because the rays of the sun collected by the bnrning glass, are all bent (as they pass through it) to one point, called the “ focus,•“ in concequence of which, the light and heat of this point are very greatly increased. Q. Why is there a dark rim round this focus ? A. Because the rays of light, which should have fallen there, are bent into the focus; and the space around (being deprived of these rays) is accordingly darkened. Q. Are all the rays bent into one point ? A. No, not quite all: and, therefore, the rim round the'focus is only slightly shadowed. Q. What is the, second chief source of Heat ? A. Electricity. Q. What is lightning ? A. Lightning is accumulated electricity discharging from the clouds (like that from a (> Leyden jar.”) Q. What causes the discharge of an eletric cloud ? A. When a cloud, overcharged with eletric fluid, approaches another - which is undercharged, the fluid rushes from the former into the latter, till both contain the same quantity, Q. Is there any other cause of lightnin" from a cloud floating near; and sometimes electric fluid rushes out of the earth into the clouds. Q. What produccss electricity in the elpuds? A. Ist— The evaporation from the earth’s surface. 2ndly—The chemical changes perpetually going on upon the earth’s surface, pud 3rdly—Currents of air of unequal temperature excite electricity by friction, as they pass by each other.