The Longitude of a place, is its distance from any given meridian, as Washington, London, or Greenwich, and is reckoned in degrees, &c. on the equator. Longitude is marked in figures, either on the equator, or at the top and bottom of the map, and can be reckoned only 180 degrees east or west, that distance being half of a circle. Longitude, on most of these maps, is reckoned from the meridian of Greenwich, near London.
The Latitude of a place is its distance in degrees, &c. north or south from the equator, and is expressed in figures on the sides of the map. Latitude can never exceed 90 degrees.
The Zones are portions of the Earth’s surface divided by the tropics and polar circles. There are five zones, viz. one torrid, two temperate, and two frigid zones. [See Map of the World, fig. 1].
The Torrid Zone is included between the tropics, and is distinguished for extreme heat, and luxuriant vegetation; the climate is generally unhealthy.
The Temperate Zones are included between the tropics and the polar circles; they have a healthy climate, and produce the greatest abundance of the most useful commodities.
The Frigid Zones lie between the polar circles and the poles, and are remarkable for extreme coldness of climate and general barrenness of soil.
A Hemisphere is half a globe. The map of the world is divided into the western and eastern Hemispheres; and the equator divides it into northern and southern Hemispheres.
The Diameter of the earth, that is, the distance through its centre, is about eight thousand miles; and its Circumference, that is, the distance round it, is about twenty-five thousand miles.
In tracing the relative situation of places, the pupil must remember to follow the direction of the parallels and meridians, and not be governed merely by the apparent direction of one place from another. Thus, on the map of the world, Iceland appears north from Newfoundland, but it is northeast. Therefore, the direction towards the top and bottom of maps is not always exactly north and south; but to go north you must proceed toward the north pole; and south, toward the south pole;—following the direction of the lines.
The preceding principles should be rendered as perfectly familiar to the pupil as the letters of the alphabet. To secure this object, the learner is required, in the following pages, to define a continent, an ocean, latitude, longitude, &c. in connexion with the subject of questions on the maps. It will also be useful, after the pupil has passed the map of the world, frequently to require similar definitions to be repeated, when naturally suggested by the subject, and thus impress the learner with the necessity of being always prepared to answer them. This method furnishes a general review of Elemental Geography through the whole course of studying the maps, and will give variety and pleasure to the exercise.