Lines, which keep always at the same distance from each other, are called parallels.

If a circle, or circular line, be conceived keeping at the same distance from the equator, it will be a parallel to the equator,

Circles of this kind are commonly drawn on the terrestrial globe, on both sides of the equator.

A circle of this kind, at 10 degrees from the equator, is called a parallel of 10 degrees.

When any such parallel passes through two places on the globe's surface, those two places have the same latitude.

Hence, parallels to the equator are called parallels of latitude.

There are four principal lesser circles parallel to the equator, which divide the globe into five unequal parts, called zones.

The circle on the north side of the equator is called the tropic of Cancer; it just touches the north part of the ecliptic, and shews the path the sun appears to describe, the longest day in summer.

That which is on the south side of the equator is called the tropic of Capricorn; it just touches the south part of the ecliptic, and shews the path the sun appears to describe, the shortest day in winter.

The space between these two tropics, which contains about 47 degrees, was called by the ancients the torrid zone.

The two polar circles are placed at the same dis

tance from the poles, that the two tropics are from the equator.

One of these is called the northern, the other the southern polar circle.

These include 23 degrees on each side of their respective poles; and, consequently, contain 47 degrees, equal to the number of degrees included between the tropics.

The space contained within the northern polar circle was, by the ancients, called the north frigid zone; and that within the southern polar circle, the south frigid zone.

The spaces between either polar circle, and its nearest tropic, which contain about 43 degrees each, were called by the ancients the two temperate zones.

PROBLEM VI. To find the latitude of any place:

If the pupil comprehends the foregoing definition, he will find no difficulty in the solution of this and some of the following problems.

Rule. Bring the place to the graduated side of the strong brass meridian, and the degree which is over it is the latitude. Thus, London will be found to have 51 degrees 30 minutes north latitude; Constantinople, 41 degrees north latitude; and the Cape of Good Hope, 34 degrees south latitude.

PROBLEM VII. To find all those places which have the same latitude with any given place.

Suppose the given place to be London; turn the globe round, and all those places which pass under the same point of the strong brass meridian, are in the same latitude.

PROBLEM VIII. To find the difference of latitude between two places.

Rule. If the places be in the same hemisphere, bring each of them to the meridian, and subtract the latitude of one from the other. If they are in different hemispheres, add the latitude of one to that of the other.

Example. The latitude of London is 51 degrees 32 minutes, that of Constantinople 41 degrees; their difference is 10 degrees 32 minutes. The difference between London, 51 degrees 32 minutes north, and the Cape of Good Hope, 34 degrees south, is 84 degrees 32 minutes.

PROBLEM IX. The latitude and longitude of any place being known, to find that place upon the globe.

Rule. Seek for the given longitude in the equator, and bring the moveable meridian to that point; then count from the equator on the meridian the degree of latitude either towards the north or south pole,

and bring the artificial horizon to that degree, and the intersection of its edge with the meridian is the situation required.

By this problem, any place not represented on the globe may be laid down thereon, and it may be seen where a ship is, when its latitude and longitude are known.

Example. The latitude of Smyrna, in Asia, is 38 degrees 28 minutes north; its longitude 27 dedegrees 30 minutes east of London; therefore, bring 27 degrees 30 minutes counted eastward on the equator, to the moveable meridian, and slide the diameter of the artificial horizon to 38 degrees 28 minutes north-latitude, and its centre will be correctly placed over Smyrna.

It may be proper, in this place, just to shew the pupil, that the latitude of any place is always equal to the elevation of the pole of the same place above the horizon. The reason of this is, that from the equator to the pole are 90 degrees, from the zenith to the horizon are also 90 degrees; the distance of the zenith to the pole is common to both; and, therefore, if taken away from both, must leave equal remains; that is, the distance from the equator to the zenith, which is the latitude, is equal to the ele、 vation of the pole.

OF FINDING THE LONGITUDE.

As the finding the longitude of places forms one of the most important problems in geography and

astronomy, some further account of it, it is presumed, will prove entertaining and useful to the reader.

"For what can be more interesting to a person in a long voyage, than to be able to tell upon what part of the globe he is, to know how far he has travelled, what distance he has to go, and how he must direct his course to arrive at the place he designs to visit? These important particulars are all determined by knowing the latitude and longitude of the place under consideration. When the discovery of the compass invited the voyager to quit his native shore, and venture himself upon. an unknown ocean, that knowledge, which before he deemed of no importance, now became a matter of absolute necessity. Floating in a frail vessel, upon an uncertain abyss, he has consigned himself to the mercy of the winds and waves, and knows not where he is*."

The following instance will prove of what use it is to know the longitude of places at sea. The editor of Lord Anson's voyage, speaking of the island of Juan Fernandez, adds, "The uncertainty we were in of its position, and our standing in for the main on the 28th of May, in order to secure a sufficient easting, when we were, indeed, extremely near it, cost us the lives of between 70 and 80 of our men, by our longer continuance at sea; from which fatal accident we might have been exempted,

*Bonnycastle's Astronomy.