of his modern disciples in a part of our country, thus addressed him':-"O sagé, condescend to enlighten me in regard to these mysteries'; how it happens that the rays, falling upon wax, cause it to drop in threads of gold', while the same heat, applied to moist clay', changes it to stoné? Or that man, moving under the full ardor of these rays, is covered with sweat', while the same heat dries up the fountains and streams'? Or, that the same light reddens the rose, stripes the tulip, blanches the lily', and browns the shepherd girl'? Whence is it that the same cause operates such opposite effects'?" The disciple of Plato ceased'; and the sage world-builder', not being able to resolve the questions of a scholar touching the most obvious matters of daily observation', retired overwhelmed with shame from the academy.

In these more fortunate days, we have in our ordinary schools young doctors of sixteen', and fair Euclids at twelvé, who, standing at the black-board during an examination', are able to discôurse, at least, learnedly' upon these points of philosophy', if they cannot satisfactorily explain them.

The great agent of these seemingly contradictory results, is a subtil, invisible fluid', of which I have already spoken', called caloric. The effect of the presence of this fluid to the perception of a sentient being', is warmth. It is supposed to expand bodies by penetrating between their molecules. In this way, a bar of red hot iron becomes perceptibly longer than when cold. A still greater quantity of caloric would have caused this bar to melt and flow, like a fluid. Whoever visits the mint will see gold and silver, by this action', become as liquid as water. Caloric, entering into the particles of water', dilates them first into steam', and then into invisible vapor. Remove this power', and the transparent fountains change to a substance like glass. To this element air owes its fluidity. The atmosphere itself would become a solid body', if caloric did not expand the molecules which compose it. It is affirmed, in these days', that philosophers have succeeded in compressing air so as to render it twice as dense as water.

Although caloric and light are frequently found in union', it is not uncommon to find them in separation. We have seen that sea-water, and many insects, offer us the brightest light without a particle of heat'; and we can heat a great number of substances without rendering them luminous. It is natural to suppose, then, that caloric and light are two

different bodies, which have a great analogy the one with the other, though many modern philosophers confound them.

The most remarkable property of caloric is its power to expand bodies'; that is to say', to augment their volume by gliding between their molecules. This effect, as I remarked at the commencement of these lectures', is directly opposed to that of the attraction of aggregation', which draws the molecules of bodies towards one another. There is, therefore, a continual war between these two forces'; and from this war results all the varied forms of matter', from the state of a solid to that of a liquid', and still further to that of an aeriform fluid.

A certain quantity of caloric, added to a solid body', changes it to a fluid. If we add still more caloric', it separates the molecules of the fluid so far from each other, that their attraction of aggregation is entirely destroyed', and the liquid is transformed into vapor or steam.

When I touch a warm body, the caloric', which is perpetually tending to an equilibrium', passes from this body into my hand. On the contrary, when I touch a cold' body, the caloric passes from my hand into that body', and I experience a sensation of cold. To the property which caloric thus has', of passing from one body to another', we owe the invention of the thermometer. The heat, in expanding the quicksilver, increases its volumè, and causes it to ascend in a small cylindrical glass vessel, marked with circles at equal distances', called a graduated scalé, by which the increase of the heat is noted.

There are bodies which heat penetrates only with difficulty. They retain' their caloric, and grant it a difficult passage. They are called bad conductors. On the contrary, bodies which give a free and easy passage to their caloric', are called good conductors. If you raise the wick of a lamp with a pin', the heat is immediately communicated to your hand. Metals are good conductors. You burn a match', on the contrary', until the flame almost touches your hand', without giving you the sensation of heat. Wood is, therefore, a bad conductor.

A little girl went into the study of Mezerai,* the celebrated historian, to get fire. Having forgotten to bring a vessel in which to carry the firé, she put some ashes in the bottom

*Mez-e-ra-i; four syllables and the fourth long,

of her hand'; and, to the great astonishment of the philosopher, put the burning coals upon the ashes', and carried off the fire in her hand. Experience had taught the child that ashes were a bad conductor of heat.

Such a sub

The warmest bodies are bad conductors. stance is a woolen dress. It keeps off the cold, not,as some suppose, by imparting warmth', but in hindering the warmth of our bodies from escaping. Hence, when the air is warmer than our bodies', a woolen dress tends to keep us cool.

Most animals, by an admirable contrivance of the Creator, are covered with wool, fur, hair, feathers', all substances among the number of bad conductors. They are clothed by the hand of Providence exactly in conformity with their wants', and the nature of things. Their dress accommodates itself to the heat of summer', and the cold of winter. It falls, and becomes thin, in the former period', and grows thicker during the winter. Aquatic birds have a species of very warm down', which only covers that part of their breast exposed to water', which is varnished with a bland oil', and is at once fortified against cold and humidity.

Nature carries her foresight still further. The same animal acquires a different fur in different climates. The northern frosts impart to the goat, rabbit, cat, and sheep', a thick and furry vestment. The same animals are almost entirely deprived of hair in the burning regions of Senegal and Guinea; while in Syriá, according to the expression of a naturalist', they are covered with a long, light, and silky vestment', like the robe of the Orientals. The wants of all beings have been calculated with such an exactness of benevolent justice that the animals, which live in valleys where they enjoy a mild temperature', are more thinly clad than the animals of mountains', that wander in the midst of storms and snow.

We might trace the same wise arrangement even in the conformation of vegetables. Their flower-buds are destined to multiply and perpetuate the species. They contain, at the same timé, the seed', the fruit', and the coming tree. Nature, neglecting nothing that could tend to preserve so important a change, has fenced the bud with scales', overlaying one another like tiles`; bristled them with hairs which defend them from insects`; and lubricated them with a light

varnish', over which the water glides without leaving a trace of humidity.

As animals are more warmly clad, by nature, in proportion as their climates are colder', so, as we approach the warm countries, these scales which envelop the germs, diminish by degrees', and end by disappearing entirely. In the torrid zone, the light buds of flowers are naked', like the savage that dances round the tree which bears them. Transfer this vegetable to our climate', and you will see nature take care to clothe and defend it by numerous scales. This is her process of acclimation.

Every thing in the universe perishes only to be renewed. Nature incessantly struggles against destruction'; and her wise and benevolent foresight maintains the equilibrium between life and death. What admirable precaution has she taken to assure the reproduction of the humblest plant! During the close of summer, she covers the ears of our maize with husks, more or less thick', according to the mildness or severity of the winter that is to follow. The naturalist discovers this provident care in many of the coverings of the fruits and grains. The savage counts the number and thickness of these coats', and is forewarned for what severity of winter he has to prepare; and, unread in the lore of our books', in reading the beautiful book of nature', he is enabled to regulate his labors', his hunting and fishing in the desert.

I hope that you have seen that the study of nature is full of charms. In proportion as you investigate her secrets, the wisdom of Providence is continually disclosed', and your views become more broad and delightful', and all dryness disappears from the pursuit of knowledge. You enjoy such a pleasure as the traveler experiences', who has finally toiled to the summit of a mountain. The prospect of boundlessness opens before him', and the heavens surround him on all sides.

LESSON LXIV.

COMPLIANCE WITH A HUSBAND'S WISHES REWARDED.

I MUST not omit to introduce at this period a department of my establishment, which, though humble in itself', wrought important effects on my after happiness.

I carried with me from my mother's house a cat', which was so beautiful that I named her * Fairy', in honor of the damsel who was changed to Grimalkin in the old romance. If I had a prejudice, it was in favor of cats' and against dogs; this was unfortunate', for, soon after my marriage', I was introduced to a mastiff of Edward's † nearly as large as myself. I had often heard him speak of this dog', and praise the faithfulness with which he guarded the office. I was too busy in other interests to think much of Growler for some time. I only observed that, on his occasional visits', (for the office was his head-quarters',) Fairy's back rose indignantly', and I felt mine disposed to mount too'. At length, Growler finding the house so comfortable, came home at night with his master', and daringly laid his unwieldy form on the center of the hearth-rug', while Fairy', routed from her luxurious station, stood upon her dignity', hissing and sputtering in one corner.

For a long period a single look from me would make Edward banish Growler from the room'; but à present of a new office-dog from a friend completely established him at homè, and my husband became accustomed to my look and Growler's presence. When he grew indifferent', my ire was roused. I affirmed that, of all created things', dogs were the dirtiest,—that the house was filled with fleas,— that my visitors could never approach the firè,-that Growler ate us out of house and homè,—and if he was to be indulged in tracking the Wilton carpet and painted floors', we had better live in a wigwam.

Edward sometimes gently excused his dog', sometimes defended him', and always turned him out of doors. The animal', knowing that he had an enemy in the cabinet', would sneak in with a coward look', his tail between his

* Pronounced Fa-ry.

+ Edward was the lady's husband.