simple circumstance of the fall of an apple, which led to the discovery of the laws upon which the Copernican system is founded; and whatever credit this system had obtained before, it now rests upon a basis from which it cannot be shaken.

Emily. This was a most fortunate apple, and more worthy to be commemorated than all those that have been sung by the poets. The apple of discord for which the goddesses contended; the golden apples by which Atalanta won the race; nay, even the apple which William Tell shot from the head of his son, cannot be compared to this!

CONVERSATION VIII.

ON THE EARTH.

Of the Terrestrial Globe.-Of the Figure of the Earth. -Of the Pendulum.-Of the Variation of the Seasons, and of the Length of Days and Nights.-Of the causes of the Heat of Summer.—Of Solar, Siderial, and Equal or Mean Time.

MRS. B.

As the earth is the planet in which we are the most particularly interested, it is my intention this morning, to explain to you the effects resulting from its annual and diurnal motions; but for this purpose it will be necessary to make you acquainted with the terrestrial globe: you have not either of you, I conclude, learnt the use of the globes ?

Caroline. No; I once indeed learnt by heart the names of the lines marked on the globe, but as I was informed they were only imaginary divisions, they did not appear to me worthy of much attention, and were soon forgotten.

Mrs. B. You suppose, then, that astronomers had been at the trouble of inventing a number of lines to little purpose. It will be impossible for me to explain to you the particular effects of the earth's motion without your having acquired a knowledge of these lines: in plate VIII. fig. 2. you will find them all delineated; and you must learn them perfectly if you wish to make any proficiency in astronomy.

Caroline. I was taught them at so early an age that I could not understand their meaning; and I have often heard you say that the only use of words was to convey ideas.

Mrs. B. The names of these lines would have conveyed ideas of the figures they were designed to express, though the use of these figures might at that time have been too difficult for you to understand. Childhood is the season when impressions on the memory are most strongly and most easily made: it is the period at which a large stock of ideas should be treasured up, the application of which we may learn when the understanding is more developed. It is, I think, a very mistaken notion that children should be taught such things only, as they can perfectly understand. Had you been early made acquainted with the terms which relate to figure and motion, how much it would have facilitated your progress in natural philosophy. I have been obliged to confine myself to the most common and familiar expressions, in explaining the laws of nature, though I am convinced that appropriate and scientific terms would have conveyed more precise and accurate ideas; but I was afraid of not being understood.

Emily. You may depend upon our learning the names of these lines thoroughly, Mrs. B.; but before

we commit them to memory, will you have the good

ness to explain them to us?

Mrs. B. Most willingly. This 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 south pole. The circle C D, which divides the globe into two equal parts between the poles, 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. There are two intermediate circles 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, or plain, is an even level surface. Let us suppose a smooth thin solid plane cut