The idea of costliness in ornament is increased by its rarity, or, rather, by its being used only where it is most conspicuous, and this sort of economy is observable even in the works of nature; for instance, the most beautiful coloured feathers of birds are on the surface, while those for use, rather than for shew, are generally of a dirty brown; it may also be observed, that those butterflies, or moths, whose wings are ornamented on the under side, generally bear them erect; while those which have the upper side most beautiful, generally spread them flat. The same remark may be extended to all the vegetable tribe; every flower, and every leaf, has one side more ornamented, more glossy, more vivid, or more highly finished than the other, and this is always the side presented to the eye. Hence we are taught, by the example of nature, not to lavish decorations where they cannot generally be seen *.
*[Good taste can only be acquired by leisure and observation; it is not, therefore, to be expected in men, whose time is fully employed in the more important acquirement of wealth or fame; while on certain subjects of taste the most elegant women often excel the most learned men; and although they may not have investigated the causes of the pleasure they either derive or communicate, yet they are more exquisitely sensible to both. This, if it were necessary, might be used as an apology for occasionally introducing allusions more familiar than the philosophic reader may deem conformable to the nature of a didactic work.]
