The sciences referred to certify further, that as regards the various forms of life there has been from the time when it can be first traced to the present day "advance and progress in the main," and that the history of the earth corresponds throughout with the history of life on the earth, while each age prepares for the coming of another better than itself. But advance and progress presuppose intelligence, because they cannot be rationally conceived of apart from an ideal goal foreseen and selected. Volumes might be written to show how subtly and accurately external nature is adjusted to the requirements of vegetable and animal life, and how vegetable and animal life are inter-related; nay, even on how well the earth is fitted for the development and happiness of man. Think of the innumerable points of contact and connection, for example, between physical geography and political economy, which all indicate so many harmonies between the earth and man's economical condition, capacities, and history.[24] [24] See Appendix XVI. The vegetable and animal kingdoms viewed generally, are also striking instances of unity of plan, of progressive order, of elaborately adjusted system. There are general principles of structure and general laws of development common to all organisms, constituting a plan of organisation capable of almost infinite variation, which underlies all the genera and orders of living creatures, vegetable and animal. It comprehends a number of subordinate plans which involve very abstract conceptions, and which even the ablest naturalists still very imperfectly comprehend. These higher plans would probably never have been thought of but for the detection of the numerous phenomena which seemed on a superficial view irreconcilable with the idea of purpose in creation. Just as it was those so-called "disturbances" in the planetary orbits, which appeared at first to point to some disorder and error in the construction of the sidereal system, that prompted Lagrange to the investigations which resulted in establishing that the order of the heavens was of a sublimer and more remarkable character than had been imagined, essentially including these apparent disturbances, so it has been the seeming exceptions to plan which are witnessed in rudimentary and aborted organs (such as the wing-bones in wingless birds, the finger-bones in horses, the legs below the skin in serpents, the teeth which never cut the gums in whales, &c.), that have indicated to modern biologists a unity of organisation far more comprehensive and wonderful than had previously been suspected. The larger and more ideal order thus brought to light as ruling in the organic world is one which could only have originated in a mind of unspeakable power and perfection. And it not only thus testifies directly of itself in favour of a Divine Intelligence, but the recognition of it, while correcting in some respects earlier