Note 8 — Chapter II
Reading edition
“The revolution of the earth is performed in a natural day, or, more strictly speaking, once in 23h. 56' 4", and as its mean circumference is 24,871 miles, it follows that any point in its equatorial surface has a rotatory motion of more than 1,000 miles per hour. This velocity must gradually diminish to nothing at either pole. Whilst the earth is thus revolving on its axis, it has a progressive motion in its orbit. If we take the length of the earth’s orbit at 630,000,000, its motion through space must exceed 68,490 miles in the hour.”—Enc. Brit. art. Physical Geography.