SAWING

This was probably man’s first method of producing fire. By rubbing two

sticks together in this way sufficient heat was produced to set fire to

easily burnable material such as dried grass, etc.]

[Illustration: DRILLING

An improvement came when man learned that by twirling a dry stick in

a hole in another piece of dry wood the fire could be started more

quickly.]

The book of wonders · 第 138 / 376 题