So that barrels and hogsheads may the more easily be rolled on them.
Are our stairs in the form of the inclined plane?
Yes; they are inclined planes with steps cut in them to make the ascent easy.
Why are house-roofs made in the form of the inclined plane?
So that the water falling on them may run off readily.
What familiar example of the inclined plane may be mentioned?
The hills, all over the country, are so many inclined planes.
Of what use are the hills?
The hills carry off the waste water from the earth, so that it is kept dry enough for plants to grow.
What other example of the inclined plane may be mentioned?