How should we feel in regard to these things?
We should feel thankful to an All-wise Creator, for having provided us with both heat and light from a never-failing source—the sun.
Expansion by Heat.
How does heat generally affect substances?
Heat expands them or makes them larger.
Does heat expand all metals?
Yes; all metals are expanded by heat.
When a rod of iron is heated, is it longer or shorter than when cold?
It is longer than when it is cold.
How do we know this?