There is still another relation of these arts to one another which must not be overlooked before proceeding further, as a knowledge of it is indispensable in forming a correct judgment of their respective merits. Like the Sciences, the Technic Arts hardly depend, after the first steps have been taken, on individual prowess for their advancement. An astronomer, a chemist, or a natural historian, now starts from the highest point reached by any of his predecessors, and he has only to observe and calculate, to analyse and put together again, in order to advance our knowledge. A giant may of course make a rapid stride in advance, but a hundred dwarfs will, if they persevere steadily in the right path, not only overtake him, but probably advance far beyond anything the most gigantic intellect can accomplish in science. So it is also in the mechanical arts. The immense strides that have of late years been made in improving all the machines employed in manufactures have not been made by the greatest intellects, but by thousands of men suggesting new contrivances and acquiring skill by steady improvement in manipulation. In ship-building, for instance, one of the most complex of the useful arts, no one can tell who the men were who converted the rude galleys in which our forefathers sailed to Crecy and Agincourt into the gigantic commercial steamers and war-ships of the present day. It was the result of thousands of intellects working steadily towards a well-defined aim, and accomplishing a triumph by a process which must always be successful in the Technic arts when persevered in long enough. [Illustration: Diagram No. 1.] The case is somewhat different with the Æsthetic arts. Some men are insensible to the harmony of colour and are not offended by the crudest contrasts. Others do not perceive concords in music, and the most violent discords give them no pain; others, on the contrary, are endowed with the utmost sensibility on these points, and are consequently not only able to appreciate the beauty of the arts arising out of colour or sound, but of advancing what to those who cannot understand them is an inexplicable mystery.