What is Porosity?

All matter has little hollows or spaces between the molecules. You know what this is in the case of a sponge, or pumice stone. Certain metals have the pores so small that it is difficult to see them except with a very powerful glass. Under great pressure water can be forced through the pores of metals, as has been done inp. 84 the case of gold. Water also is porous, but the spaces between the molecules are very small.

Excerpt from:
Title: Practical Mechanics for Boys
Author: J. S. Zerbe

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