The Rollo Series (Volume 11) (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1835. Excerpt: ... CHAPTER VII. THE MEASURE OF PRESSURE. When Rollo got home, he found that his father had not yet come, and that supper was not quite ready; and so he thought he would go and meet his father. He accordingly toolc his hoop, and ran out of the gate into the road, hoping that he might overtake James, who, he supposed, could not have gone very far. He did not overtake him, for James had left the main road to go home by a cross path, through the woods and fields. So Rollo went on alone, trundling his hoop, until he came to a bridge which led over a brook, which the road had to cross. He stopped here, and leaned over the railing of the bridge, to look down into the water. It was a large brook, and there was a mill apon it, at a little distance below. There was a dam at the mill. There is always a dam where theie is a mill upon a stream of water, to keep back the water, and make it rise high in the pond above the dam. The pond above this mill-dam extended back nearly to the bridge, so that the water under the bridge was not a rapid stream, tumbling and foaming along; but it was deep and almost still. " Now," said Rollo to himself, " I can tell whether the water is level. I'll throw a stick in." His idea was, that, if the water was level, there would be no current; but that, if there was any current, so as to float the stick slowly down under the bridge, then there would be a current made by the water's seeking its level. So he threw in a little stick. At first, it floated a little way up the stream, being driven by the impulse which he had given it, in throwing it. But it moved more and more slowly, as its momentum--that is, the force with which it was moving--was gradually extinguished by the resistance of the water, and then it began slowly to move the other way...