ANIMAL KINGDOM.

Mollusca, or Soft Animals.

THE Mollusca have neither an 'articulated skeleton nor a vertebral canal, and their nervous system is not united in a spinal marrow, but dispersed in different parts of the body.

FOOT-HEADED ANIMALS compose the first class of the second great division or sub-kingdom of animals. The body, in some, resembles a bag or pouch, from which proceeds a well-developed head, having two large eyes, and a number of long fleshy appendages, by which they crawl, swim, and seize their prey.

They swim with the head backwards, and crawl in all directions with the head beneath or above the body. They are very voracious, and destroy a great number of other pulpy animals, crust-covered animals, and fish. These are the only pulpy animals in which organs of hearing have been discovered, and whose brain is enclosed in a gristly box.

This class is divided into six tribes, two of the principal of which are called cuttle-fish, and nautili. Cuttle-fish have no shell, and are remarkable for having a gland containing a very black liquid, by which they can darken the surrounding water, when they wish to escape from an enemy. It is supposed that Indian or Chinese ink is made from this liquid.

Some are very large, and sufficiently powerful, in their own element, to conquer a dog. They often conceal themselves in a hole in a rock, and stretch out their long arms to seize any prey that may come within reach. Nautili inhabit beautiful shells, some of which have no divisions, and others are partitioned off into numerous cells or chambers. Two of the eight arms with which the paper-nautilus is furnished, are broad and membraneous, and are used by the animal as sails.

FIN-FOOTED ANIMALS form the second class. They have wing or fin-like feet on the sides of the neck, by which they swim; and are destitute of any other appendages. They are so 'transparent that the internal organs can be seen through the skin, and most of them inhabit a shell likewise considerably transparent, thin, and beautifully coloured. Many of them rise to the surface of the sea about midnight, and disappear as the day breaks. They are all small, yet a few kinds of them constitute the principal food of the whale. Very few of them have eyes.

BELLY-CREEPING ANIMALS compose the third class, which embraces a great number of animals differing much from each other, but agreeing in having a fleshy disk on the belly that enables them to crawl. Slugs, snails, and a great variety of shell-fish, belong to this class.

HEADLESS ANIMALS compose the fourth class of pulpy animals. They have no apparent head, but merely a concealed mouth. They all live in the water, and most have a shell consisting of two pieces, improperly called valves.

The celebrated 1oriental and other pearls are obtained only from the shells of these headless animals. This class is divided into two tribes, the first of which is by far the most numerous, and contains all kinds of oysters, muscles, and cockles.

ARM-FOOTED ANIMALS form the fifth class. Instead of feet they have two arms furnished with numerous 1 filaments, which they can extend from or draw into the shell at pleasure. The shell is composed of two valves, and is immovable. But three tribes are known.

HAIR-FOOTED ANIMALS, known as barnacles and acorn-shells, compose the sixth and last class. They are always attached to rocks, ships' bottoms, pieces of floating timber, or even to shell-fish, turtles, and whales.

Vide page 17, notes. Second Sub-Kingdom

T

Vide Root.

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ARABIA AND THE SARACENS.

THE Arabs have always been wandering tribes, and have dwelt in tents amid the trackless deserts which cover a large portion of their country. Their early history is very imperfectly known. The first event that is worth recording, was the birth of 3 Mahomet. This took place at Mecca, a city on the borders of the Red Sea, in the year 570 of the Christian era.

Till the age of twenty-five, Mahomet was a cameldriver in the desert. He afterwards spent much of his time in solitude. His dwelling was a lonesome cave, where he pretended to be employed in prayer and meditation. When he was forty years old, he set up for a prophet.

Those of the Arabians who followed Mahomet were called 4 Saracens. After their leader's death, they conquered the whole of Turkey in Asia, and many other countries. The capital of their empire was the city of Bagdad, on the river Tigris.

One of the successors of Mahomet was Ali, his son-inlaw. He was opposed by Ayesha, Mahomet's widow. This woman was suspected of having murdered her

husband.

She raised an army, and led them to battle against Ali. During the conflict, Ayesha sat in a sort of cage or litter, on the back of a camel. The camel's rein was

1. Vide Root. 2. Arabs principally descended from Ishmael, Gen. xvi. 12. 3. Mahometans date from A.D. 622, the year of the Hegira, or flight of Mahomet from Mecca to Medina; hence also the crescent as their emblem, the moon being then in that state. Mahomet died by poison, A.D. 632. 4. From Sara in

Arabia. 5. Caliph means a successor. The title included both spiritual and civil jurisdiction, and was used during 656 years, till Bagdad was taken by th Tartars.

held by one of her soldiers; and it is said that seventy soldiers were killed, one after another, while holding the rein. Finally, Ali was victorious, and confirmed his sway over all the disciples of Mahomet, and over the countries which they had won.

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Here the Saracen empire was established. The kings were called caliphs. They reigned at Bagdad for the space of six hundred and twenty years. One of them was Mahmud Gazui. He was a great conqueror, and added a part of India to his dominions.

He

The last of the caliphs was named Mostasem. was so proud and vain-glorious, that he considered his subjects unworthy to behold his face. He therefore never appeared in public without wearing a veil of golden tissue. Whenever he rode through the streets, thousands would flock to get a glimpse of his golden veil.

But at length Hulaki, chief of the Tartars, took the city of Bagdad. He stripped off the golden veil of the caliph Mostasem, and put him alive into a leathern bag. The bag, with the poor caliph in it, was dragged by horses through the same streets where he had formerly ridden in triumph.

Thus perished the caliph Mostasem, being bruised to death on the pavements. With him ended the empire of the Saracens, in the year 1258 of the Christian era.

GEOGRAPHICAL.-Area, 1,000,000 square miles. Population, ten millions.
What are the boundaries of Arabia?

Between what lines of latitude and longitude is it situated?

How are mounts Horeb and Sinai situated, and the cities Mecca, Medina, Sana, Mocha, and Aden?

What is the difference in time between London and Mecca?

Trace the course of the Moors from Arabia to Spain

CHRONOLOGICAL.-Hagar retires to the wilderness with Ishmael, B.C. 1892.

Joseph sold to the Ishmaelites, B.C. 1728.

Israelites, led by Moses, enter the wilderness, B.C. 1491.

CHEMISTRY.

Caloric-Electricity—Magnetism.

THE direct effect of caloric, when it enters a body, is to dilate or expand it, as in the case of mercury in a thermometer. You warm the instrument in your hand or by the fire, and the mercury swells and rises; put it in a cold place, it contracts and falls down the tube: and hence the use of the thermometer in measuring heat. Heat lengthens the pendulum, and makes the clock go slower. Half fill a bladder with air, and tie it tightly, heat it, and you will expand the air, and burst the bladder. Caloric radiates, as we feel when we stand before a fire; it is reflected, as in the Dutch ovens. It will pass through different bodies with more or less facility, according as they are good or bad conductors. Put the end of a long bit of iron in the fire, the other end becomes hot; put a bit of wood or glass of the same length, and the heat will not pass so quickly,-hence the tinker has a wooden handle to his soldering iron.

Caloric is a powerful chemical agent. Metals that are to be mixed must first be melted. Heat favours solution,

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which is an important process, and one by which soluble bodies are brought into contact, that they may act on one another. 1 Evaporation, by which we obtain bodies from their solutions, is done by caloric, as in obtaining salt from the salt pans. It is by evaporation from the sun's heat that water rises from the ocean, forming clouds, which by subsequent condensation becomes rain.

Volatilization is another effect of caloric, as when spirit is obtained by distillation, or carbon is volatilized in our fires and condenses in our chimneys as soot.

Electricity is much concerned in chemical changes; by it compounds may be formed or decomposed. Put hydrogen and oxygen into a bottle together, they do not