"I have often wondered why it is that there is so much driftwood on the western shore of this stream, and hardly any on the eastern shore."
Blakely, his attention having been drawn to it, remarked that he had found this to be the case in a number of streams, not only on the island, but elsewhere.
"That is a singular thing," replied the Professor. "It is accounted for by the rotation of the earth, which is from west to east. The rotation of the earth in that direction also accounts for the prevailing trade winds which are from the east to the west."
"In what way should the rotation of the earth cause the drift to move westwardly?"
"There are two forces which act on a free object on the surface of the earth, namely, centrifugal and centripetal. The first named is that action which tends to throw an object outwardly, like dirt flying out from a rapidly moving wheel; and the latter action is that which draws inwardly. Thus the spokes might be likened to centripetal force. The attraction of gravitation in the earth is the centripetal force, and its rotation produces the centrifugal force. When an object, like a plumb bob, or an article floating on the water is free to move, it is found to lag behind the movement of the earth surface, this retarding movement being sufficient to cause it to creep to the west, with the result you have noticed."
The hill pointed out by Blakely was fully three miles west of the river. The four boys, Ralph, Tom, Jim and Will, with Blakely and the Professor, all armed with guns, made a party strong enough to enable them to successfully withstand the attack of any animal, and it was proposed to[p. 165] make a trip through a portion of the forest, so as to get some idea of its character.
To carry out this plan, their course was directed to the west, and within an hour and a half were well in the thick of the wood. The first thing that attracted the attention of all were the magnificent trees, among them a species of pitch pine, together with immense redwood trees, and numerous oak species abounded.
Before they had penetrated a mile the first animals were seen. They had never been hunted, as the natives kept away from the forest fastnesses, and it was singular to see the familiarity of the animals. An immense panther, or tree leopard, fascinated the boys, and they maneuvered to get close enough for a shot. He was very wary, however, and Blakely and the Professor kept in the background while the boys stalked him from tree to tree, and finally Ralph had him in range and fired.
He crashed down but alighted on his feet, and without waiting for any explanations bounded over to the spot where Ralph and Will were crouched behind a fallen tree. Will saw the movement and called to Jim and Tom, and the latter, taking careful aim, fired, without, apparently, checking the animal.