_Mrs. B._ Most willingly. This figure of a globe, or sphere, represents the earth; the line which passes through its centre, and on which it turns, is called its axis, and the two extremities of the axis A and B, are the poles, distinguished by the names of the north and the south pole. The circle C D, which divides the globe into two equal parts between the poles, and equally distant from them, is called the equator, or equinoctial line; that part of the globe to the north of the equator, is the northern hemisphere; that part to the south of the equator, the southern hemisphere. The small circle E F, which surrounds the north pole, is called the arctic circle; that G H, which surrounds the south pole, the antarctic circle; these are also called polar circles. There are two circles, intermediate between the polar circles and the equator; that to the north I K, called the tropic of Cancer; that to the south, L M, called the tropic of Capricorn. Lastly, this circle, L K, which divides the globe into two equal parts, crossing the equator and extending northward as far as the tropic of Cancer, and southward as far as the tropic of Capricorn, is called the ecliptic. The delineation of the ecliptic on the terrestrial globe is not without danger of conveying false ideas; for the ecliptic (as I have before said) is an imaginary circle in the heavens, passing through the middle of the zodiac, and situated in the plane of the earth's orbit. _Caroline._ I do not understand the meaning of the plane of the earth's orbit. _Mrs. B._ A plane, is an even flat surface. Were you to bend a piece of wire, so as to form a hoop, you might then stretch a piece of cloth, or paper over it, like the head of a drum; this would form a flat surface, which might be called the plane of the hoop. Now the orbit of the earth, is an imaginary circle, surrounding the sun, and you can readily imagine a plane extending from one side of this circle to the other, filling up its whole area: such a plane would pass through the centre of the sun, dividing it into hemispheres. You may then imagine this plane extended beyond the limits of the earth's orbit, on every side, until it reached those fixed stars which form the signs of the zodiac; passing through the middle of these signs, it would give you the place of that imaginary circle in the heavens, call the ecliptic; which is the sun's apparent path. Let fig. 1. plate 9, represent such a plane, S the sun, E the earth with its orbit, and A B C D the ecliptic passing through the middle of the zodiac. [Illustration: PLATE IX.] _Emily._ If the ecliptic relates only to the heavens, why is it described upon the terrestrial globe?