The diametrical opposite of this dominant Christian art is the new artistic tendency which has been developed during the present century in connection with science. The remarkable expansion of our knowledge of nature, and the discovery of countless beautiful forms of life, which it includes, have awakened quite a new æsthetic sense in our generation, and thus given a new tone to painting and sculpture. Numerous scientific voyages and expeditions for the exploration of unknown lands and seas, partly in earlier centuries, but more especially in the nineteenth, have brought to light an undreamed abundance of new organic forms. The number of new species of animals and plants soon became enormous, and among them (especially among the lower groups that had been neglected before) there were thousands of forms of great beauty and interest, affording an entirely new inspiration for painting, sculpture, architecture, and technical art. In this respect a new world was revealed by the great advance of microscopic research in the second half of the century, and especially by the discovery of the marvellous inhabitants of the deep sea, which were first brought to light by the famous expedition of the _Challenger_ (1872-76). Thousands of graceful radiolaria and thalamophora, of pretty medusæ and corals, of extraordinary molluscs, and crabs, suddenly introduced us to a wealth of hidden organisms beyond all anticipation, the peculiar beauty and diversity of which far transcend all the creations of the human imagination. In the fifty large volumes of the account of the _Challenger_ expedition a vast number of these beautiful forms are delineated on three thousand plates; and there are millions of other lovely organisms described in other great works that are included in the fast-growing literature of zoology and botany of the last ten years. I began on a small scale to select a number of these beautiful forms for more popular description in my _Art Forms in Nature_ (1899). However, there is now no need for long voyages and costly works to appreciate the beauties of this world. A man needs only to keep his eyes open and his mind disciplined. Surrounding nature offers us everywhere a marvellous wealth of lovely and interesting objects of all kinds. In every bit of moss and blade of grass, in every beetle and butterfly, we find, when we examine it carefully, beauties which are usually overlooked. Above all, when we examine them with a powerful glass or, better still, with a good microscope, we find everywhere in nature a new world of inexhaustible charms.