785a.-TABLE I.

ELEMENTS OF THE ORBITS OF MERCURY, VENUS, THE EARTH, AND MARS, FOR INTERVALS OF 20,000 YEARS, FROM 100,000 YEARS BEFORE A.D. 1800 TO 100,000 YEARS AFTER THAT EPOCH.

20,000 7 38 10 2 12 52 2 44 12

80,000 6 30 20 4 52 37 18 58 1 55 12 60,000 7 17 30 4 4 10 2 36 42 I 1 41 40,000 7 25 30 o 53 8 4 3 I 2 46 15

2 46 37 O 7 о 63 23 28 0 O о 1 51 6 +20,000 6 29 50 2 8552 7 46 0 53 49 + 40,000 6 8 40 o 55 44 2 27 53 3 49 +60,000 5 49 10 2 28 36 o 51 52 4 10 49 + 80,000 5 33 20 2 5 43 1 45 40 1 46 11 + 100,000 5 35 20 0 21 54 3 2 57 0 49 45

1

786.-TABLE II.

DISTANCES OF THE PLANETS FROM THE SUN AND EARTH IN MILLIONS OF MILES.

(The numbers in this Table can be read as millions and decimals of a million, or, by adding three ciphers on the right in each column, as millions and thousands: for example, the mean distance of Mercury from the Sun is 35-392 in the Table, or 35,392,000 miles.)

It has not been considered necessary to give in this table the distances of all the minor planets from the sun and earth. Those of Flora, whose mean distance is the nearest, and Camilla, the farthest from the sun, will give a general idea of the position of the group in the solar system. The nearest approach to the sun is made by Phocea, while Freia recedes farthest from him, the difference of distance between Phocea in perihelion, and Freia in aphelion being about 204 millions of miles.

A general impression of the relative magnitudes of the different planets is conveyed to the mind by a simple illustration first suggested by Sir J. Herschel. Suppose we take a globe, two feet in diameter, and place it in a well-levelled field or bowling-green, Let this globe represent the sun. Then at the relative distances of the planets, Mercury will be represented by a grain of mustard seed; Venus, a pea; the Earth, also a pea; Mars, a rather large pin's head; the minor planets as grains of sand; Jupiter, a moderately-sized orange; Saturn, a small orange; Uranus, a fullsized cherry, or small plum; and Neptune, a middle-sized plum.