duces a greater tide while it is in the meridian above the horizon, than when in the meridian below it. When in the southern hemisphere the reverse is the case.

For the same reason, when the moon is in the southern signs, the greatest tides on the other side of the equator will be when it is below the horizon, and the least tides when it is above it.

The ebb and flow of the sea would happen uniformly, and with great precision, were the whole surface of the earth covered with water; but since there is a multitude of islands, and two vast continents, which interrupt the natural course of the water, a variety of appearances are to be met with in different places, which cannot be explained without regarding the situation of shores, shoals, rivers, and other objects which contribute in producing these appearances. About small islands and headlands in the middle of the ocean the tides rise very little, but in some bays and in the mouth of rivers they rise from 12 to 50 feet.

The spring tides are highest and the neap tides lowest about the beginning of the year; for the earth being nearest the sun about the first of January, must be more strongly attracted by that body than at any other time hence the spring tides which happen about that time will be greater than at any other.

;

The tides in the Pacific ocean exceed those of the Atlantic, and they are less in that part of the Atlantic which is within the torrid zone, between Africa and America, than in the temperate zones; because the ocean is there much broader. For the tides tohave full flow, the ocean should be ninety degrees wide, that being the distance between the greatest elevation and greatest depression.

and moon together 10 feet, when at their mean distance from the earth, and about 12 feet when the moon is at her least distance. 3. When the moon forms an angle of 90 degrees with the sun, namely, in her first and third quarters.

HOLLAND AND BELGIUM.

THE 'Netherlands, or Holland and Belgium, were formerly one country. The whole 'territory is bounded on the north by the North Sea, east by Germany, south by France, and west by the British Channel and the North Sea. These territories belonged at one time to Rome, afterwards to Germany, and finally to Spain.

In 1581, the seven northern provinces revolted against Philip of Spain, and formed themselves into a republic, which was then called Holland. During the seventeenth century it was a very powerful nation, especially by sea. At this time her ships often disputed, and sometimes successfully, with the British fleets.

Holland was once overrun by the sea, but it is now walled out by vast dikes. These enormous sea ramparts, which are erected all along the coast, are mostly about thirty feet in height, and seventy feet broad at the bottom. They are built of clay, faced on the land side with wood and stone, and toward the sea with mats of rushes and sea-weed.

The face of the country is flat. From the top of a steeple, the eye ranges over a boundless plain, 'intersected by canals and dikes; meadows of the freshest 'verdure covered by numerous herds of cattle; towns, villages, and detached houses embosomed in trees; numerous vessels continually gliding along the canals, and by the animation which they give to the landscape,' compensating in some degree for its want of bold and picturesque beauty.

Amsterdam, the capital, one of the largest cities in Europe, stands on an arm of the Zuyder Zee, called the

1. Vide Root. 2. Netherlands, lower lands; and Holland, hollow or low land, nearly all of it being lower than the sea.

River Y. The whole city is built upon piles, driven inte the ground.

There are three universities in Holland, and there are elementary schools in all the towns and villages.

The government is a constitutional 'monarchy, with some resemblance to the British, although the two houses of assembly are much less powerful than the British commons and peers.

The remaining provinces of the Netherlands, called Belgium, or the Low Countries, remained in the possession of the Spaniards after the independence of Holland. Early in the eighteenth century the country passed into the hands of the Austrians, and was held by them till the breaking out of the French revolution, when it was conquered by the French, and incorporated with France in 1795.

After the overthrow of Napoleon, it was united to Holland, and the two countries formed the kingdom of the Netherlands: this union was effected at the Congress of Vienna. The Belgians were dissatisfied with this arrangement, and in 1830 they revolted. The independence of Belgium was subsequently acknowledged by the five great European powers. The Belgian congress made choice of Prince Leopold, of Saxe Coburg, for king, who accepted the crown, and took his oath to the constitution at Brussels, the capital, on the 21st of July, 1831.

GEOGRAPHICAL.-Area, 25,977 square miles. Population, Holland three millions, Belgium four millions.

How is Holland bounded?

Write the names of the principal towns of Holland.

What Dutch towns stand on the Rhine and the Maese?

Why has Holland so few rivers?

What are the boundaries of Belgium, and its principal towns?

What are the latitude and longitude of Amsterdam and Brussels?

CHRONOLOGICAL.-Belgic provinces united to Dutch provinces under Spanish

dominion, 1548.

Belgic provinces ceded to Austria, and called Austrian Netherlands, 1717.

Belgic and Dutch provinces united to form the kingdom of the Netherlands, 1815 Separated again and declared independent, 1830.

ASTRONOMY.

Comets.

BESIDES these planets already mentioned, there are some other bodies which revolve round the sun, called comets. They move in very 'eccentric ellipses, and their periods of revolution are so long, and so little known, that few are ever observed twice. They are only seen by us when they are in that part of their orbit which is nearest to the sun, and then they move so fast, that they soon become again invisible to us.

The number of comets is unknown; numbers of small ones have been discovered by telescopes. Their distances are inconceivably great, and most of them move entirely beyond the planetary orbits; though some have descended below Mars.

Their appearances are very different.

Some appear

only a faint vapour; others have a 'nucleus or solid part in the middle. When they approach the sun, they put forth the appearance of a beard or tail of luminous matter, which is sometimes of astonishing length. These tails are always directed from the sun.

There are three comets, those of 1680, 1744, and 1759, which require particular notice. The comet of 1680 was remarkable for its near approach to the sun; so near, that in its 2 perihelion it was not above a sixth part of the diameter of the luminary from the surface of it. The tail, like that of other comets, increased in length and brightness as it came nearer to the sun, and grew shorter and fainter as it went farther from him and from the earth, till that and the comet were too far off to be longer visible.

The comet of 1744 was seen at Lausanne in Switzerland, December 13th, 1743. From that time it increased in brightness and magnitude as it was coming nearer to the

sun.

Its diameter when at the distance of the sun from

us, measured about one minute, which brings it out equal to three times the diameter of the earth. The comet of 1759 did not make any considerable appearance, by reason of the unfavourable situation at the time. markably fine comet appeared in the end of the year 1811, and continued visible during the beginning of 1812.

A re

It is believed that there are at least twenty-one comets belonging to our system, moving in different directions. All those that have been observed, have moved through the ethereal regions and the orbits of the planets, without suffering the least sensible resistance to their motions, which sufficiently proves that the planets do not move in solid orbits.

Comets were formerly supposed to be prodigies or portents, and to foretell some great event or revolution, such as the fall of empires, or the death of some eminent or distinguished personage; but they are now known to have no more connexion with the civil or political affairs of the world than any other of the heavenly bodies.

1

The conjectures which have been advanced by several celebrated astronomers respecting the nature and cause of the tail which usually accompanies a comet, show that they are not understood. Tycho Brache supposed that the tail was occasioned by the rays of the sun passing through the head or nucleus of the comet, which he believed to be semi-transparent. Kepler thought that it was the atmosphere of the comet which was driven behind it by the force of the solar rays. Sir Isaac Newton considered that the tail was a thin vapour ascending by means of the sun's heat, as smoke does from the earth. Probably not one of these conjectures is right; and the nature, uses, and laws of comets, are left for future discovery.

1. Vide Root. 2. The part of the orbit nearest the sun; aphelion, the farthest. Hevelius declared that the orbits of comets were parabolic, and Halley that they re. turned periodically. Kepler's law of passing over equal areas in equal times is truo of the comets as of the planets.