"Do you remember," asked Mr. Wilson, "how I proved that?""Oh, I remember," said Fred. "It is useless to try and join the two edges of a broken plate or saucer, or any other solid body, by pressing them together, because we cannot bring all the particles into actual contact, and without actual contact there can be no cohesion. But it is possible to join two perfectly smooth and level sheets of glass by pressing them together. All their particles are in actual contact, and cohesion acts and joins them.""Are we to understand, sir," asked Willie, "that cohesion acts only between the molecules of the same kind of substance?""Yes," said Mr. Wilson, "the molecules of solid bodies are held together by cohesion, and the molecules of liquids are also held together by cohesion. When we mix two glasses of water, they immediately mingle and form a compact whole, because the molecules are brought into actual contact with each other on all sides."Lesson 03
Our Bodies