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196 Artificial flowers, of which such beautiful specimens may now be had, make an elegant, becoming, and fashionable ornament, and are strongly to be recommended for the outside of bonnets or hats; they should not, however, come in contact with the skin, as their lovely colours are too often produced by the aid of very poisonous dyes.

The head, unless in extreme climates, does not require a very warm covering. As I have said, man requires clothing because he has not the natural protection of wool or hair possessed by the lower animals; but on our heads we have a natural protection in the shape of hair, and it is considered a beauty if we have this in considerable quantity.

The reason why we have hair in abundance on our heads alone is interesting, not only from an evolutionary point of view, but also because it teaches us a lesson in the choice of head-gear.

When speaking of the ways in which we lose heat, I mentioned that, among others, we lose it by convection—the rising of heated particles. Now, in this way, heat is naturally lost chiefly from the uppermost surface of the body, and we consequently find that most land animals have their hair or wool thicker on their backs than on their bellies. The particles of air heated by their bodies, which, having become more elastic in the process of heating, have a tendency to rise and give place to colder particles, are entangled in the hair or wool, and thus adhering to the body, make it a small warm atmosphere of its own; for air is a