Miller's Mind training for children Book 3 (of 3) / A practical training for successful living; Educational games that train the senses

by William Emer Miller

Hardness of Substances

It is often valuable to know the degree of hardness of different substances, and these can easily be remembered by the following list. In degree of relative hardness the list is as follows, the hardest coming first.

Diamond	Apatite
Corundum	Bell Metal
Topaz	Boric Acid
Quartz	Rock Salt
Iridium	Kaolin

Take Kaolin as a basis. The number opposite each substance in the following list indicates its comparative degree of hardness in relation to Kaolin:

1	Kaolin	TIE	See tie on Kaolin
2	Rock Salt	SNOW	Poured over Rock Salt
3	Boric Acid	HOME	Built of Boric Acid
4	Bell Metal	WIRE	Swinging a Bell
5	Apatite	WHEEL	With a big appetite for running
6	Iridium	SASH	Irritating the wearer
7	Quartz	EGG	Quartz taken from an Egg
8	Topaz	IVY	To pass the Ivy
9	Corundum	WHIP	Made Cora run
10	Diamond	TOES	Set with Diamonds

In the list you have ten substances. Kaolin, the base, is 1, Rock Salt is 2, which indicates that Rock Salt is twice as hard as Kaolin. Iridium is 6, and six times as hard as Kaolin. Diamond is 10, which means that it is ten times as hard as Kaolin.

Learning this list by picturing reminders with the word of the Code list will enable you to easily recall these ten substances and the degree of hardness compared with Kaolin.