Every body of matter is composed of very fine particles that fill the space occupied by the body. The particles of some bodies are held more closely together than are those of others, and we express this difference by stating that some bodies are more or less porous than others. A body whose particles are not very close together is said to possess porosity. Unglazed earthenware will absorb water.

The property of a substance which enables it to withstand long wear without decay or change is called durability. Painted oak, for instance, is a very durable wood, as it will stand a great deal of hard usage.

A substance which resists heat and will melt only at a high temperature is said to possess the property of infusibility. Platinum possesses a higher degree of infusibility than any other metal. The following table shows the order of malleability, ductility, tenacity, and infusibility of the most common metals. Those possessing these properties to the highest degree appear at the tops of the columns.

Table Showing the Order of