Chapter 11 Exercise 16, Page 223

Exercise 16

Page 223

Early Mirrors

Mirrors are not a modern invention; they have been used since the stone age. The first mirrors were made from rocks.

A special type of stone was needed: obsidian. This is a volcanic glass that is found in lava. To make the mirror, the stone was ground down on one side with another stone until the surface is flat.

Then it was polished repeatedly, until it became extremely shiny. At that point, the surface was highly reflective, and people were able to see themselves.