Page 257 - Third Book of Reading Lessons

256 THIRD BOOK OF
to the water, you suddenly stop the wagon, the water, in endeavouring to continue the state of motion, rises up on the opposite side. In like manner, if, while you are sitting quietly on your horse, the animal starts rward, you will be in danger of ing o backward; but if, while you are galloping along, the animal stops on a sudden, you will be liable to be thrown rward.
OHARLEs.-This I know by experience, but I was not aware of the reason of it till to-day.

uses of the principles of natural philosophy, is, that they may be applied to, and will explain, many of the common concerns of li .
LESSON XVIII.
LAWS OF MOTION (CONTINUED).
F THER.-We now come to the second law of mo­ tion, which is,-" that the change motion is pro­ portional to the force impressed, and in the rection
thatforce."
OH RLEs.-There is no di culty in this ; r i
, while my cricket-ball is rolling along after Henry has struck it, I strike it again, it goes on with in­ creased velocity, and that in proportion to the strength which I exert on the occasion; whereas, i while it is rolling, I strike it back again, or give it a side­ blow, I change the direction of its course.
FATHER.-In the same way, gravity, and the re­ sistance of the atmosphere, change the direction of a cannon-ball om its course in a straight line, and
F THER.-One of the rst, and not least important