An old form consisted of pellets of a very poisonous mercurial compound which gave off dangerous fumes when heated. The "eggs" may be made of comparatively safe material by the following formula:

Potassium bichromate. 2 parts

Potassium nitrate..... 1 part

White sugar.......... 2 parts

Powder each ingredient separately, mix, and press into small paper cones. These must be kept from light and moisture.

Of course, neither this nor other chemical toys containing substances in the slightest degree harmful if swallowed should be placed in the hands of children not old enough fully to understand the danger of eating or even tasting unknown things.