moisture, becomes by wonderful agencies sap in the sapvessels, to nourish every part, the air being made to act upon the sap through the lungs, that is the leaves. From the varying chemical agencies of different plants in different soils and climates, arise the varying products; almost the same simple principles producing them all. The sugar of the sugar cane, the oxalic acid of sorrel, the starch in potato or grain, and gum arabic, all consist of precisely the same elements, oxygen, hydrogen, and carbon, but in different proportions. There are other vegetable principles known among chemists, as extract: liquorice may be considered an instance, and so may gum, jelly, and saccharine matter; also vegetable acids, as acid of lemon; fixed vegetable oils, as oil of olives, sweet oil, or linseed oil; volatile vegetable oils, as oil of cinnamon, oil of nutmeg, and otto of roses; upon these last chiefly depend the taste and smell of the plants containing them; resins, as amber, gamboge, myrrh, aloes, &c.; starch or farina, as flour. All these may be resolved into oxygen, hydrogen, and carbon. During the life of plants, great chemical changes take place, which in many instances are imitated by us in the arts. Fruits are first nearly tasteless, as when gooseberries are first brought to market; then by the chemical agency of the sunny warmth, &c. the oxygen, hydrogen, and carbon are differently arranged, and acid is produced; the fruit is now sour. Leave it longer on the bush, and still further changes take place; the same elements that formed the acid, again differently arranged, form sugar, the gooseberry is sweet, it is said to be ripe; leave it longer, the power of vitality loses its control over the chemical changes, the elements disperse themselves, forming compounds altogether different: the fruit is now subject to what is called the putrefactive fermentation. 1. Vide Root. 2. Forming carbonate of lime, which is insoluble in water PERSIA. To the Death of Xerxes. THE first inhabitants of Persia were descended from Elam, the eldest son of Shem. They were therefore called 2 Elamites. Very little is known of their history till about eighteen centuries after the deluge. Cyrus, a great conqueror, then ascended the throne of Persia. Cyrus continued to extend his empire in all directions. Media, Parthia, Mesopotamia, Armenia, Syria, Canaan, and part of Arabia, were subdued, and made portions of his kingdom. In the taking of Babylon, and the destruction of its king Belshazzar, he fulfilled the judgment pronounced by the prophet Daniel. 4 The walls of this great city were so thick and high, that it would have been impossible for an enemy either to break them down, or to climb over them. It was therefore a very difficult matter to take this strong place. The channel of the river Euphrates ran directly through the centre of Babylon. Cyrus caused deep ditches to be dug around the city, so that he could draw off all the water of the river, and leave the channel dry. On a certain night, Belshazzar, king of Babylon, made a great festival. His guards, and nearly all the inhabitants, were eating and drinking, thoughtless of the enemy on the outside of their walls. The Persians seized this opportunity to throw open the dams of the ditches. The whole water of the Euphrates immediately flowed into them. Cyrus put himself at the head of the Persian army; and where the mighty river had so lately rushed 1. Vide Root. 2. The Persians call their country Iran. 3. B. C. 569, prophesied of by Isaiah, by name, xliv. 28, and xlv. I, upwards of a century before his birth. 4. Daniel v. 28. along, there were now the trampling footsteps of an innumerable host. Thus the Persians entered the city. Cyrus afterwards marched against the Scythians, a brave nation who dwelt to the north-east of the Caspian Sea. But Tomyris, their queen, collected an army, and fought a battle with the Persians. Cyrus was defeated, and taken prisoner, and afterwards killed. Another king of the Persians was named Darius. He was a cruel tyrant. While Darius was preparing to make war on Greece, he fell sick and died. His successor was his son Xerxes. This monarch invaded Greece with nearly two millions of men on land, and more than half a million on board his fleet. At Thermopylæ, Xerxes wished to lead his army through a narrow passage between a mountain and the sea. Leonidas, king of Sparta, opposed him with six thousand men. Seventy thousand Persians were slain in the attempt to break through the pass. At last Leonidas found that the Persians could not be kept back any longer. He therefore sent away all but three hundred men, and with these he remained at the pass of Thermopyla. The immense host of the Persians came onward like a flood; and only one soldier of the three hundred escaped to Sparta to tell that the rest were slain. But Xerxes did not long continue to triumph. His fleet was defeated at Salamis, and his army at Platæa. Not long after his return to Persia, the proud Xerxes was murdered. This event happened about the year 465 His son Artaxerxes made peace with the Greeks. B. C. GEOGRAPHICAL.-Ancient Persia, in its greatest extent, included all between the Hellespont, or Dardanelles, and the river Indus; and between the Caspian Sea and the Indian Ocean. What states and great cities are now included within these boundaries? What lakes, rivers, and mountains are within these limits? What places did the army of Xerxes pass through, in going to Athens? CHRONOLOGICAL.-Cyrus, the founder of the Persian empire, 559-529 B.C. CHEMISTRY. Its Application to Practical Purposes. CHEMISTRY teaches us, among other things, that nothing is lost, that there is no destruction in nature, but almost infinite and constant changes. By study and art, we favour, modify, or arrest these changes, so as to make the result useful to man. Brewing is a chemical process. Many important changes take place after plants have nearly or entirely lost their vitality. Take barley as an instance; the maltster first, by an artificial process, converts the starch of it into sugar; and then afterwards the brewer takes this malt, and by his process changes the solution of sugar into beer. The chemical changes taking place in this last process constitute what is called vinous fermentation. The oxygen and carbon form carbonic acid, (the suffocating gas rising in the tubs,) while other oxygen, carbon, and hydrogen combine, and form spirit or alcohol, which is the basis of all these strong liquors. In what is called 'panary fermentation (bread making), sugar is converted into alcohol and carbonic acid; the latter being rendered volatile by heat, escapes through the bread, and makes it porous, or light, as it is called. If instead of shutting up wine and beer in close vessels, we allow fermentation to proceed, other changes take place. By what is called the acetous fermentation, a different ordering of the elements oxygen, hydrogen, and carbon takes place, and vinegar is formed. Allow it still further to go on, and putrefaction, the dispersion of the elements, is the result. Putrefaction may be restrained by 'chlorine, which is therefore called an anti'septic, or by sealing in close vessels, by which means even such a compound of vegetable and animal as soup may be preserved for many months, or even years. Anımal matter is the most prone to putrefaction. Colours used in dyeing are chiefly vegetable, and of themselves would not often remain in the cloth, or be as it is called fast, but by certain salts of tin, &c. technically called mordants, with which the cloth is prepared, strong affinity is secured, and the object attained. Tanning is a chemical process. The skins of animals consist almost entirely of an animal matter called gelatine. But in oak bark there is a vegetable matter called tannin; the skin if soaked in a solution of the tannin, will become hard and tough, in fact it becomes leather. Besides this gelatine, there are other principles in animal matter, such as albumen, the white of egg. Much of this is contained in blood; it will coagulate by heat, a property taken advantage of by the sugar refiner, who throws bullock's blood in with his sugar: the heat coagulates the albumen of the blood, which entangling the foul matters of the sugar, rises with them to the surface, and is skimmed off. Mucus, which is saliva,-fibrin, which is animal fibre, best seen in a piece of coarse beef,-resin, sugar, as well as oil and acids, are all in animal bodies; and these in their turn are again composed of oxygen, hydrogen, carbon, and nitrogen, which as we have before said, are called simple elements. When such great changes result merely from a body having an atom more or an atom less of a particular element, shall we be surprised to find that the decay of vast 'accumulations of vegetable matter produces coalthat the old worn-out mine becomes again replenished when the elements 'percolate through the earth, and intermingle? We learn in fact this from chemistry, that the decay of existing animals and vegetables, disperses the elements which help to form future races. 1. Vide Root. |