Part 50 (2/2)

Gravity is the attraction between the earth and the bodies on the earth, which ht of bodies

What do you understand by specific weight or gravity?

It ht of an equal bulk of some other body taken as a standard--commonly water

Why do we say that certain old--are heavier than others, say, lead or iron?

Because the forravity

But is not a pound of gold as heavy as a pound of lead?

Yes; but a luold will be heavier than a lump of lead of equal bulk

Can we explain by this e call floating?

A body will float in water if its gravity is less than that of water; for example, wood floats for this reason in water, and a balloon in the air

Why does a portion of the floating body sink below the surface of the water?

Because the body in order to float ht to the whole floating body

But why do iron stea heavier than water?

Because the steamer is not a solid piece of iron, but is hollow, and so increased in bulk; for that reason the weight of the vessel and its contents is less than that of an equal bulk of water

How can you ascertain that air has weight?

We can do it by the barometer and by very many experiences in daily life If one end of a straw be dipped into a vessel of water and the other end be sucked, the liquid will rise to the mouth There we see the pressure of the outside air forces the liquid through the strahere the air was re

Can you show the same by another instrument?

Yes; the common water pump demonstrates the same as the straw A tube is placed into the water, the air is sucked out from the tube by the moveh the tube

What are Artesian wells?

Wells so named because they were made first at Artois, in France They work on the principle that every liquid seeks its level Of the rain which falls, a part soaks into the soil of h which it cannot pass, it will collect and be stored up If a hole be bored into this reservoir the water will rise in it

Do you know some other properties of air?