Page 255 - Third Book of Reading Lessons

254 THIRD BOOK OF
stones in the arcade, that we can scarcely shoot with
a rce small enough.
EMM .- nd I remember Charles and my cousin. were, last winter, trying how r they could shoot their marbles along the ice of the canal; and they went a prodigious distance in comparison of that which they would have gone on the gravel, or even on the pavement in the arcade.
F THER.-Now, these instances, properly applied, will convince you,-that· a body once put in motion, would go on r ever, if it were not compelled by some external rce to change its state.
OH RLES.-I perceive what you are going to say:
/ -it is the rubbjng or ±i:iction of the marbles against the ground which does the ·business. For, on the pavement there are wer obstacles than on the grav­ el, and wer n the ice than on the pavement; and hence you would lead us to conclude, that if all ob­ stacles were removed, they might proceed on r ever. But what are we to say of the ball; what stops that?
F THER.-Besides iction, there is another and still more important circumstance to be taken into consideration, which a ects the ball, marbles, and every body in motion.
OnARLEs.-I understand you ; that is the attraction of gravitation.
FATHER.-It is; r, from what we said when we conversed on that subject, it appeared that gravity has a tendency to bring every body in motion to the earth; consequently, in a w seconds your ball must come to the ground by that cause alone; but, besides the attraction of gravitation, there is the resistance which the air, through which the ball moves, makes to its passage.