A Guide To The Scientific Knowledge Of Things Familiar Part 1

A Guide to the Scientific Knowledge of Things Familiar.

by Ebenezer Cobham Brewer.

PREFACE.

Of all science, none is more generally interesting than that which explains the common phenomena of life. We see that salt and snow are both white, a rose red, leaves green, and the violet a deep purple; but how few persons ever ask the reason why! We know that a flute produces a musical sound, and a cracked bell a discordant one--that fire is hot, ice cold, and a candle luminous--that water boils when subjected to heat, and freezes from cold; but when a child looks up into our face and asks us "why,"--how many times is it silenced with a frown, or called "very foolish for asking such silly questions!" The object of the present book is to explain about 2000 of these "silly questions" (which are often more easily asked than answered) in language so simple that a child may understand it, yet not so childish as to offend the scientific; and in order that the answers may be strictly correct, not only the most approved modern authors have been consulted, but the ma.n.u.script has been submitted sheet by sheet to the revision of two gentlemen of acknowledged reputation for scientific attainments. To the REV. A. BATH POWER, M. A. especially, great obligation is due, for a careful revision of the whole ma.n.u.script, for many excellent hints, and useful additions. In conclusion, so much diligence has been bestowed upon this little work for nearly ten years, so much useful information has been supplied by scientific friends, and so minute a revision has been made of every answer, that it is no presumption to express a hope that this "Guide to the Scientific Knowledge of Things Familiar" will become generally useful and acceptable, not only to the young, but to those advanced to maturer life.

In this work some questions occur more than once, because they serve to ill.u.s.trate different principles; and whenever cognate questions occur, the answers have been rendered as similar as possible, in order to a.s.sist the memory of the learner.

PART I.

HEAT.

INTRODUCTION.

Q. _What is heat?_

A. The sensation of warmth.

Q. _How is this sensation produced?_

A. When we touch a substance of higher temperature than ourselves, the warmer substance keeps parting with its heat, till both are of equal temperature.

Q. _What is that "stream of heat" called, which flows thus, from one body, to another?_

A. CALO'RIC. _Caloric_, therefore, is the _matter of heat_, which pa.s.ses from body to body; but HEAT is the _sensation, of warmth_, produced by the influx of Calo'ric.

Q. _What are the four princ.i.p.al_ SOURCES _of heat_?

A. 1.--The Sun. 2.--Electricity. 3.--Chemical Action: and 4.--Mechanical Action.

Q. _What are the princ.i.p.al_ EFFECTS _of heat_?

A. Expansion, Liquefaction, Vaporization, and Ignition.

CHAPTER I.

Q. _What is the_ PRINc.i.p.aL _source of Heat_?

A. The SUN.

Q. _Why do_ BURNING GLa.s.sES _set fire to substances submitted to their power_?

A. The rays of the sun, collected by the Burning Gla.s.s, are all _bent to one point_, called the "focus;" thus the heat and light, (which should be diffused over the _whole_ gla.s.s,) being gathered together into one 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 s.p.a.ce 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.

CHAPTER II.

Q. _What is the second chief source of heat?_

A. ELECTRICITY.

Q. _What is_ LIGHTNING?

A. Lightning is only an _Electric Spark, taken from the clouds_.

Q. _What causes the discharge of an electric cloud?_

A. When a cloud, _overcharged_ with electric fluid, approaches another which is _under-charged_, the fluid rushes from the former into the latter, till both have the same quant.i.ty.

Q. _Is there any OTHER cause of lightning, besides the one just mentioned?_

A. Yes; sometimes mountains, trees, and steeples, will discharge a lightning cloud floating near; and sometimes electric fluid rushes out of the _earth_, into the clouds.