mountain in Britain? It is Ben Macdui in Aberdeenshire, which is 4400 feet. How are valley's caused? They owe their form to the elevation of the strata on each side. Is the ocean continuous around the globe? The ocean consists of one vast volume of water, which may be said completely to surround the globe. Is its level every where the same? It has been ascertained that the mean height of the Pacific above the Atlantic is about three feet and a half. What causes may influence a difference of level? They may be owing to tides and currents, by which the ocean is continually agitated. What gives the peculiar saltness to the water of the ocean? It derives its peculiar taste from certain salts dissolved in it. Enumerate the saline substances. These consist of muriate of soda or common salt, muriate of magnesia, and muriate of lime. What is the source of moisture on the land? From the surface of the sea there is continually ascending a portion of its water in the form of vapour, which mingles with the air, and which mounting to the higher parts of the atmosphere, forms clouds, and at last descends in rain upon the earth. How are clouds characterized? The highest are called cirri, the middle clouds cumuli, and the lower stratus or mists, and nimbi or rain clouds. What is the cause of springs and rivers? As it is a property of all fluids to descend until they attain the lowest levels, the water flows through the fissures till it attains the opening at the base of the mountain, where it issues in the form of a spring or a river. How are lakes formed? They are found in the hollow basins of mountains or valleys, which being shut up, allow the waters of springs to accumulate. Which are the largest rivers in the world? The Amazons and La Plata in South America, the Mississippi in North America, the Ganges in India the Danube, the Don and the Rhine in Europe. Which

C

are the most remarkable water-falls? The falls of Niagara are the most extensive and magnificent in the world.

ASTRONOMY.

Astronomy, of all the natural sciences, presents the most extensive series of discoveries. By observing for ages and determining with exactness the positions of the sun, moon, and stars, by tracing and measuring with precision their various motions, and by employing all the resources of mathematical science in investigating the constant laws to which these motions are subject, the human mind has succeeded in passing from the first cursory view of the heavens to that comprehensive survey by which, in the present state of astronomical science, we contemplate the past and future states of the system of the universe. This is a science of the highest interest and utility to the young. It is a subject on which a certain portion of information should be communicated to the young of all classes at school.

What is the meaning of the word Astronomy? It is derived from two Greek words, astron, a star, and nomos, a rule or law, and therefore signifies the laws of the stars. What does this science teach? It teaches the names and places of all the most remarkable stars, as also the motions of the sun and all the planets. How many kinds of planets are there? Two; namely, primary and secondary. What kind of motion has the sun? The sun has a motion round his own axis. Have the planets also a motion round their own axis? Yes. Is this rotatory motion uniform or variable? Uniform. Have the planets and the sun any other kind of motion? Yes; the sun and all the planets revolve around their common centre of gravity. Is the common centre of gravity

of the sun and planets within or without the sun's body Within. What are the orbits of the planets round the sun called? Ellipses. Is the motion of a planet in its orbit uniform or variable? Variable. When is the motion of a planet in its orbit quickest, and when slowest? The motion is quickest when the planet is nearest the sun, and slowest when it is at its greatest distance from the sun. What names are given to the points of the orbits nearest and remotest from the sun? The point of the orbit which is nearest to the sun is called the perihelion, and the furthest point is called the aphelion. What name is given to the straight line supposed to be drawn across the orbit from the perihelion to the aphelion? It is called the major axis. What do you call the line supposed to be drawn from the centre of the sun to the centre of a planet? This line is called the radius vector. Is the centre of the sun placed in the centre of a planet's orbit? No; it is placed in one of its foci. Is the length of the radius vector always the same, or does it vary? The length of the radius vector is constantly varying, being shortest when the planet is in perihelio and longest when it is in aphelio. What are the fundamental laws of the planetary motion called ? They are called Kepler's laws, having been discovered by a philosopher of this name. How many of these laws are there, and what are they? Kepler's laws are three in number, namely, 1. The orbit of every planet is an ellipse; 2. The areas which the radius vector passes over in any given time are proportional to those times. 3. The squares of the periodic times of the sidereal revolution of any two planets, are to each other in the proportion of the third powers of their mean distances from the sun. Do the secondary planets revolve round the sun? No; they revolve round the primary planets to which they belong, and describe elliptic

orbits, being thus primary planets in the focus; and they also follow all Kepler's laws. What are the secondary planets called? They are called satellites. What is the meaning of the word planet and the word satellite? The word planet signifies wanderer, and the word satellite signifies attendant. Is the moon a satellite? Yes; it is the only secondary planet which attends on the earth. How many primary planets are there, and what are their names? There are eleven primary planets, and they are called Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus, Ceres, Pallas, Juno, and Vesta. The first six have been known from time immemorial; the remainder have all been discovered since the year 1780. Are all these planets visible to

the naked eye? No; the last five are visible only by Are all the satellites visible to

means of a telescope.

You have

the naked eye? No; none but our moon. said that the orbits of the satellites are ellipses; what are the extreme points of the major axis of the moon's orbit called? The point nearest to the earth is called the perigee, and the furthest point is called the apogee. What is the derivation of the words perihelion, and aphelion? They are derived from the Greek peri, about or near to, apo, away from, and helios, the sun. And what is the derivation of the word apogee and perigee ? They are similarly derived from apo and peri as above, and gee, the earth.

NATURAL HISTORY.

What does the study of natural history embrace? It embraces a description of every object on the surface of the globe and its internal cavities, in the ocean, and in the air or atmosphere by which our world is surrounded. What are the branches into which it is usually divided?

Into Geology and Mineralogy, Botany and Zoology. Wherein do bodies possessing life differ from dead or inanimate matter. Bodies possessing life have a regularly organised structure, by which they can prepare nourishment for their growth and produce other beings of their own kind. They have also the power of motion and sensation. Are plants and vegetables living bodies? Yes; they have a certain degree of life and structure, but have no sensation like animals. What are the conditions of bodies necessary to preserve life? A certain degree of moisture or fluidity seems necessary to life, and a certain degree of heat seems essential; for many animals are torpid during cold and revive with heat. Are there many kinds of animated beings? Yes; an immense variety from the worm up to man, whose body is so admirably framed. How many different

kinds of animals are there? Naturalists have described at least eighty thousand. Why should there have been so many different kinds of animals formed? The beneficent Creator has so willed that life and enjoyment should pervade every part of the world which he has called into existence, and thus we find the air and the water swarming with their respective myriads. What is the general structure of animal bodies? All animals have a muscular structure. By the power of these muscles, which act by a contraction and relaxation of their fibres, they move, walk, fly, seize their food, and defend themselves from their enemies. All animals have a stomach. There is also a nervous system by which animals have sensation and irritability; and in the higher animals a brain, a heart for the circulation of blood through the body, lungs for the breathing of air, and a framework of bones to give the body solidity and strength. Is there any thing else to be remarked in the general appearance of animals? Most animals