The artist who is illustrating a great theme upon a large spread of canvas finds it necessary from time to time to lay down the brush, with which he is accurately filling in the more delicate minutiæ, that he may retreat to a distance and view his picture as a whole. It is essential to the higher development of his art that he should not omit this comprehensive survey. The same thing holds good in Literature and Science, as well as in Art. The historian must, from time to time, take a fresh survey of History as a whole. If he neglect to do so, the group of figures to which he devotes his special attention will certainly not take up its true position among the other groups that appear on the canvas of History. The man of science, also, should not forget that he is, according to his individual bent or capacity, aiding in the construction of a great Philosophy; and he should now and again turn aside from the microscope, or lay down the hammer, to take a more comprehensive survey of that Philosophy, whose aim it is to comprehend and consolidate the widest generalizations of Science.