The peasants when they used to tell the tale by the hearth fire said the shoe was made of glass.

This was in mediaeval Europe, at a time when glass was much more of a rarity.

The material was chosen to imply a sort of jewelled strangeness from the start.

When Cinderella loses it in her haste, it should flee at once like a white mouse, to hide under the sofa.

It should be pictured there with special artifice, so that the sensuous little foot of every girl-child in the audience will tingle to wear it.