"For what is your life? It is even a vapour, that appeareth for a little time, and then vanisheth away."-JAMES IV.

the caloric may be said to be squeezed, or forced out. The effect depends upon the nature of the body compressed, the force of compression employed, &c. If the force is great, considerable heat, attended by a spark, will be the result.

A blacksmith may hammer a small piece of iron until it becomes red hot. With this he may light a match, and kindle the fire of his forge. The iron has become more dense by the hammering, and it cannot again be heated to the same degree by similar means, until it has been exposed in fire, to a red heat. Is it not possible that, by hammering, the particles of iron have been driven closer together, and the latent heat driven out? No further hammering will force the atoms nearer, and therefore no further heat can be developed. But when the iron has again absorbed caloric, by being plunged in a fire, it is again charged with latent heat. Indians produce sparks by rubbing together two pieces of wood. Two pieces of ice may be rubbed together until sufficient warmth is developed to melt them both. The axles of railway carriages frequently become red hot from friction.

369. Why does evaporation produce cold?

Evaporation is the opposite effect to condensation. When the atoms of bodies are forcibly compressed, the caloric hidden among them is driven out; when the atoms of bodies are expanded, as in evaporation, heat is absorbed. Hence evaporation is always attended by cold, and condensation by heat.

370. Why are wet clothing and damp beds dangerous?

Because, when the water which causes the dampness evaporates, it takes away a large amount of caloric from the body, reducing its temperature below the healthy standard.

371. Why does eau-de-cologne give relief to persons suffering from feverish headache?

Because the spirit of the eau-de-cologne is very volatile; and when it is spread over the temples, it instantly flies off, bearing away a great amount of caloric, and affording a refreshing feeling of coolness.

A person might be frozen to death during very warm weather, by pouring upon his body, for some time, sulphuric ether, and keeping him exposed to a thorough draught of air. The winds on the borders of the Persian Gulf are often so scorching that travellers are suddenly suffocated unless they cover their heads with a wet cloth; if this be too wet, they immediately feel an intolerable cold, which would prove fatal if the moisture was not speedily dissipated by heat.

"Yet man is born to trouble, as the sparks fly upward. I would seek unto God, and unto God would I commit my cause." "-JOB V.

Because the portion of water which oozes through to their surfaces evaporates therefrom, and bears away the caloric of the varied water.

373. Why, if the "cooler" be placed in the sun, will the water become colder than otherwise?

Because the heat of the sun, instead of passing through the cooler, is carried away by the rapid evaporation of water from the surface of the vessel; and in this rapid evaporation, the caloric of the contained water is also partly drawn off.

The blacks in Senegambia have a similar method of cooling water by filling tanned leather bags with it, which they hang up in the sun; the water oozes through the leather so as to keep the outward surface wet, which, by its quick and continued evaporation, cools the water remarkably.

374. Why does the collision of flint and steel produce sparks?

The density of the substances of the flint and steel facilitates the driving out of caloric by a sharp blow. If the particles of those bodies were soft and yielding, the caloric would simply be driven from one part of their substance to another. But as their atoms cannot easily be disturbed, the compression caused by a smart blow drives the caloric out at the surface, as the readiest point of escape.

375. Why must the blow be very instantaneous to produce a spark?

Because the substances of both flint and steel, and especially of the steel, are good conductors, and would quickly conduct away the excess of heat produced at any one point, But the smartness of the blow, while it compresses the atoms of those bodies in the highest degree, produces heat so suddenly that it cannot escape by conduction.

What an eloquent lecture might be delivered upon the old-fashioned Tinderbox, illustrated by the one experiment of "striking a light." In that box lie, cold and motionless, the Flint and Steel, rude in form and crude in substance. And yet, within the breast of each, there lies a spark of that grand element which influences every atom of the universe; a spark which could invoke the fierce agents of destruction to wrap their blasting flames around a stately forest,

"I know that whatsoever God doeth, it shall be for ever: nothing can be put to it, nor anything taken from it; and God doeth it that men

should fear before him."-ECCLES. III.

or a crowded city, and sweep it from the surface of the world; or which might kindle the genial blaze upon the homely hearth, and shed a radiant glow upon a group of smiling faces; a spark such as that which rises with the curling smoke from the village blacksmith's forge-or that which leaps with terrific wrath from the troubled breast of a Vesuvius. And then the Tinder-the Cotton-the Carbon: what a tale might be told of the cotton-field where it grew, of the black slave that plucked it, of the white toiler who spun it into a garment, and of the village beauty who wore it-until, faded and despised, it was cast amongst a heap of old rags, and finally found its way to the tinder-box. Then the Tinder might tell of its hopes; how, though now a blackened mass, soiling everything that touched it, it would soon be wedded to one of the great ministers of nature, and fly away on transparent wings, until, resting upon some Alpine tree,, it would make its home among the green leaves, and for a while live in freshness and beauty, looking down upon the peaceful vale. Then the Steel might tell its story, how for centuries it lay in the deep caverns of the earth, until man, with his unquiet spirit, dug down to the dark depths and dragged it forth, saying, "No longer be at peace." Then would come tales of the fiery furnace, what Fire had done for Steel, and what Steel had done for Fire. And then the Flint might tell of the time when the weather-bound mariners, lighting their fires upon the Syrian shore, melted silicious stones into gems of glass, and thus led the way to the discovery of the transparent pane that gives a crystal inlet to the light of our homes; of the mirror in whose face the lady contemplates her charms; of the microscope and the telescope by which the invisible are brought to sight, and the distant drawn near; of the prism by which Newton analysed the rays of light; and of the photographic camera in which the sun prints with his own rays the pictures of his own adorning. And then both Flint and Steel might relate their adventures in the battle-field, whither they had gone together, and of fights they had seen in which man struck down his fellow-man, and like a fiend had revelled in his brother's blood. Thus, even from the cold hearts of flint and steel, man might learn a lesson which should make him blush at the 'glory of war;" and the proud, who despise the teachings of small things, might learn to appreciate the truths that are linked to the story of a "tinderbox."

376. Why is caloric produced by friction?

Because, as in the case of the flint and steel, the compression of the particles of the bodies between which the friction is produced, sets free their latent caloric.

But, in the case of friction, another fact must be considered, which is, that caloric has a tendency to flow towards a point of excitement. Thus the first heat produced by friction would arise from the escape of the caloric of the surfaces rubbed together; but as the action continued, the heat would increase, because caloric would begin to flow from the more distant portions of the excited bodies to the point of excitement.

"Yea, I will gather you, and blow upon you in the fire of my wrath, and ye shall be melted in the midst thereof."-EZEKIEL XXIII.

377. Why do forests sometimes take fire?

Because in dense woods the branches of trees, when moved by the violence of the winds, are rubbed together, producing the degree of friction necessary to ignite them.

378. How can caloric be disengaged by electricity or galvinism?

A more intense degree of caloric may be obtained by the aid of an electrical battery, or by the galvanic apparatus, than by any other means. But the relation between heat and electricity is not at present understood. Electricity produces heat, and heat electricity-the "reason why " is one of the grand problems remaining open for solution by those master-minds that love to pursue the theorems of scientific inquiry.

379. Why is caloric produced by chemical mixture?

Because when chemical action takes place, the atomic condition of bodies undergoes a change. Whenever fluid particles assume a more solid form, heat is given off. When water is poured upon quick-lime, the water unites to the lime and forms a solid body; the caloric which caused the fluidity of the water is given off, and a great amount of heat is evolved.

380. What is the caloric which exists in bodies usually called?

It is called latent caloric, or, sometimes, the caloric of fluidity.

381. Why is it sometimes called the caloric of fluidity?

Because, wherever it exists largely, the body in which it exists is in a fluid condition, and this condition is attributed to the presence of the amount of caloric.

382. Why is caloric sometimes called “free ?”

The term free caloric is applied to it whenever it is uncombined with any substance. If we heat a poker until it becomes red hot, that amount of caloric which is taken up by the poker, in excess of what was latent in it before, may be regarded as free caloric; for, as it is not combined with the iron, it will quit it directly that the

"The words of his mouth were smoother than butter, but war was in his heart."-PSALM LV.

poker is removed from the fire, and will diffuse itself by passing from the poker by radiation, or by other means, and entering into whatever colder bodies may come within the reach of its influence.

383. How can latent caloric and free caloric exist in a body at the same time?

This may be easily explained by the familiar example of a piece of common bread which has been dipped in water. The bread will contain two portions of water-one of them in a state of combination, forming a part of the bread; the other only interposed between the particles of the bread, and capable of being squeezed out by pressure.

384. What substances contain latent caloric?

Caloric in a latent state exists in all substances in nature.

385. Do all substances contain the same amount of latent caloric?

No; caloric combines with different substances in very different proportions; and for this reason, one body is said to have a greater capacity for caloric than another.

386. What is meant by the term "capacity for caloric?"

If a lock of wool and a piece of sponge of equal size be dipped in water, the sponge will take up a larger amount of water than the wool, and hence it may be said that the sponge has a greater capacity for water than the wool.

387. Is the capacity for caloric uniformly the same in the same bodies?

The same bodies have at all times an equal capacity for caloric; but when a change occurs in the state of those bodies, then their capacity alters.

Whenever a body changes its chemical state, it either combines with, or separates from, caloric.

388. Why, in making butter, does it become warm at the moment when the cream changes from a fluid to a solid? Because the heat, which was latent in the cream in its fluid