"To gaze," says Dr. Hudson, "into that wonderful world which lies in a drop of water, crossed by some stems of green weed, to see transparent living mechanism at work, and to gain some idea of its modes of action, to watch a tiny speck that can sail through the prick of a needle's point; to see its crystal armour flashing with ever varying tint, its head glorious with the halo of its quivering cilia; to see it gliding through the emerald stems, hunting for its food, snatching at its prey, fleeing from its enemy, chasing its mate (the fiercest of our passions blazing in an invisible speck); to see it whirling in a mad dance, to the sound of its own music, the music of its happiness, the exquisite happiness of living--can any one, who has once enjoyed this sight, ever turn from it to mere books and drawings, without the sense that he has left all Fairyland behind him?"[49] The study of Natural History has indeed the special advantage of carrying us into the country and the open air. Lakes are even more restful than rivers or the sea. Rivers are always flowing, though it may be but slowly; the sea may rest awhile, now and then, but is generally full of action and energy; while lakes seem to sleep and dream. Lakes in a beautiful country are like silver ornaments on a lovely dress, like liquid gems in a beautiful setting, or bright eyes in a lovely face. Indeed as we gaze down on a lake from some hill or cliff it almost looks solid, like some great blue crystal. [Illustration: WINDERMERE. _To face page 254._] It is not merely for purposes of commerce or convenience that men love to live near rivers. Let me live harmlessly, and near the brink Of Trent or Avon have my dwelling-place; Where I may see my quill, or cork, down sink, With eager bite of pike, or bleak, or dace; And on the world and my Creator think: While some men strive ill-gotten goods t' embrace: And others spend their time in base excess Of wine; or worse, in war, or wantonness. Let them that will, these pastimes still pursue, And on such pleasing fancies feed their fill: So I the fields and meadows green may view And daily by fresh rivers walk at will, Among the daisies and the violets blue, Red hyacinth and yellow daffodil.[50] It is interesting and delightful to trace a river from its source to the sea.