Because the former have a greater specific gravity.


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

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


Can we explain by this what we 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 must displace a portion of water
equal in weight to the whole floating body.


But why do iron steamers float--iron being 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.