A. The sensation of warmth.

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.

A. Calo’ric. Caloric, therefore, is the matter of heat, which passes from body to body; but Heat is the sensation, of warmth, produced by the influx of Calo’ric.

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

A. Expansion, Liquefaction, Vaporization, and Ignition.

A. The Sun.

A. The rays of the sun, collected by the Burning Glass, are all bent to one point, called the “focus;” thus the heat and light, (which should be diffused over the whole glass,) being gathered together into one point, are very greatly increased.

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.

A. No, not quite all: and, therefore, the rim round the focus is only slightly shadowed.

A. Electricity.

A. Lightning is only an Electric Spark, taken from the clouds.

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 quantity.

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.

A. 1st—The evaporation from the earth’s surface.

2ndly—The chemical changes perpetually going on: and

3rdly—Currents of air of unequal temperature, excite electricity by friction, as they pass by each other.

A. Electrical clouds are the lowest of all clouds; they are rarely more than 700 yards above the ground; and sometimes, they actually touch the earth with one of their edges.

A. In a fine day, the clouds are often 4 or 5 miles above our head; but the average height of the clouds is from 1-1/2 to 2 miles.

A. When the lightning-cloud is a long way off, the resistance of the air is so great, that the electrical current is diverted into a zig-zag course.

A. As the lightning condenses the air, in the immediate advance of its path; it keeps flying from side to side, in order to pass where there is the least resistance.

A. The air is condensed by the rapidity of the lightning-flash.

A. Whatever resists the flash, diverts its course; and when terrestrial objects offer resistance to the current, they are in great danger of being destroyed.

A. Sometimes (in very severe storms) a flash of lightning will divide into two or more parts; and then each branch assumes the zig-zag form.

A. When the lightning-cloud hovers near the earth, as the flash meets with very little resistance, it is not diverted; or (in other words) the flash is straight.

A. It is only the reflection of distant flashes, not distinctly visible: and sometimes several flashes (from different clouds) intermingle, and form one vast blaze or sheet of lightning.

A. The ball of fire is by far the most dangerous; and the zig-zag lightning is next in danger. Sheet lightning is not often attended with danger.

A. Because (whenever they fall) much mischief is occasioned by their bursting, which they always do, with an explosion like that of a cannon.

A. Yes; they often run a considerable way along the ground, then stop for a little time, and burst in numberless pieces: sometimes each of these pieces will explode; and at other times, the whole ball will burst at once, producing most mischievous consequences.

A. They will set houses and barns on fire; and kill all cattle and human beings, which happen to be in their course.

A. When the electric current passes through a man or beast, it produces so violent an action upon the nerves, that it destroys life.

A. Only when his body forms a part of the lightning’s path: i. e. when the electric fluid (in its way to the earth) actually passes through his body.

A. Because lightning strikes with amazing force, whatever opposes it: and if a man stand in the way, it strikes him such a blow, as to maim him.

A. Lightning parts the air through which it passes; and when the parted air closes again, the noise made by the concussion, is called Thunder.

A. Iron is a conductor, and therefore allows the fluid to go freely through it: but air being a non-conductor, resists the lightning; which, therefore, rips it open, in order to pass through it.

A. When the lightning-cloud is near the earth, as the flash is straight,—the whole volume of air (through which it passes) collapses at once; and produces one unbroken sudden crash.

A. When the rent air closes again, it is said to collapse.

A. When the lightning-cloud is a long way off, as the flash is zigzag, the air does not collapse all at once; and as we hear the concussion of one part after another, the peal is broken, protracted, and irregular.

A. That part nearest the earth; then the strata above; and last of all, that in the immediate vicinity of the cloud.

A. If a board were laid upon the earth, and several other boards were piled upon it, this pile would represent strata of wood.

A. A layer of air covers the earth; another layer rests upon it; and thus layer is piled upon layer, for 50 miles in height. Each layer is a “stratum” of air; and the plural of stratum is strata.

A. Because sound takes a whole second of time to travel 380 yards; but the air is ripped from top to bottom instantaneously: if, therefore, the cloud were 1000 yards off, we should hear the collapsing of the lowest strata nearly three seconds, before we heard that in the immediate vicinity of the cloud.

A. When the storm is far distant, the thunder sounds like a deep growl.

A. Yes; the flatter the country, the more unbroken the peal: Mountain scenery breaks the peal, and makes it harsh and irregular.

A. The rolling is produced by the reverberation of the thunder along the massive clouds.

A. The echo.

A. The cloud collapses, as soon as the electric fluid has left it; and the water it contained is squeezed out.

A. The flash rent the air asunder through which it darted; and when the two parts collapse, a rapid motion is produced, which we call wind: the vibration of the thunder contributes also to agitate the air.

A. The quivering motion it gives to the air, by its loud sound.

A. Because the lightning-clouds are so far off, that the sound of the thunder is lost, before it reaches the earth.

A. No; the notion of thunder-bolts falling from the clouds, arises from the globular form, that is sometimes assumed by a flash of lightning.

A. The flash travels nearly a million times faster than the thunder; if, therefore, the thunder has far to come, it will not reach the earth till a considerable time after the flash.

A. Yes; the flash is instantaneous, but the thunder will take a whole second of time to travel 380 yards: hence, if the flash is 5 seconds before the thunder, the cloud is 1900 yards off.

(i. e. 380 × 5 = 1900 yards.)

A. It is very dangerous to be near a tree, or lofty building; it is dangerous also, to be near a river, or any running water.

A. Because a tall pointed object, (like a tree or spire,) will frequently discharge a lightning-cloud; and then the electric fluid will pass down it, in its way to the earth.

A. A lightning-cloud (floating over a plain) may be too far off to be discharged by it; but as a tree, or spire, would shorten the distance between the cloud and its conductor, it might no longer be too far off a conductor to be discharged.

A. No; dry air is not a conductor of lightning; and therefore, the flash rends it in twain, to get to some conductor.

A. Because the electric fluid (called lightning) always rushes down the outside of the tree or spire; and if any one were standing near, might pass through him, and kill or maim him.

A. It rolls down the outside of a tree; but passes through the inside of a man.

A. Lightning always makes choice of the best conductors; and the outside of a tree is a better conductor than the inside.

A. As the fluids of the human body make a better conductor than the skin, therefore lightning passes through a man, and not down the skin.

A. Because running water is a good conductor; and lightning always takes in its course the best conductors.

A. Because the height of a man may be sufficient to discharge a cloud: and (if there were no taller object nigh) the lightning might make the man its conductor to the water.

A. For two reasons: 1st—Because the steeple may discharge the lightning-cloud, in consequence of its mere height.

2ndly—The swinging of the bells causes a current of air, which collects electric fluid.

A. The rapid motion of running causes a current of air, which collects electric fluid, and is often fatal.

A. The fire-place, (especially if the fire be lighted); the attics and cellar. It is also dangerous to sit close by the walls; to ring the bell; or to bar the shutters, during a thunder-storm.

A. Because the heated air and soot are conductors of lightning; especially when connected with such excellent conductors as the stove, fender, and fire-irons.

A. Lightning sometimes passes from the clouds to the earth, and sometimes from the earth to the clouds; and therefore, the middle story of a house is always the safest to be in, during a thunder-storm.

A. When the clouds are in a “negative” state of electricity.

A. When the clouds are in a “positive” state of electricity.

A. When the clouds contain more electric fluid than they generally do, they are said to be in a positive state of electricity.

A. When the clouds contain less electric fluid than they ought to do, they are said to be in a negative state of electricity.

A. Always from a positive body, or one over-burdened with electric fluid.

A. It is called the “returning stroke;” because the earth (being over-burdened with electric fluid) returns the surplus quantity to the clouds.

A. Because the electric fluid sometimes runs down the wall of a house or room; and (as a man is a better conductor than a brick wall), would make him its path, and injure him.

A. Bell-wire is an excellent conductor; and (if a person were to touch the bell-handle), the electric fluid, passing down the wire, might run through his hand and injure it.

A. Because the human body is a better conductor than the wall (between the bell-handle and the floor); and as lightning always chooses the best conductors for its path, it would (in this case) pass through the man, and injure him.

A. The iron shutter-bar is an excellent conductor; and (if a person were touching the bar), the electric fluid passing down it, might run from the bar through the person touching it, and injure him.

A. For two reasons. 1st—Because a mass of people form a better conductor than an individual: and

2ndly—The vapour from a crowd increases the danger of such a place.

A. Each living body is a conductor of electricity; and a connected mass of such conductors is more likely to be struck, than a single individual.

A. Vapour is a conductor, and therefore, may determine the shock; especially when connected with so many living bodies.