Again, the connecting points of the arms and legs with the trunk of a human body afford the most perfect types of universal joints which nature has produced. The man-made universal joint has a wider range of movement, possesses greater strength, and is more perfect mechanically. A universal joint is a piece of mechanism between two elements, which enables them to be turned, or moved, at any angle relative to each other. But why multiply these instances. Like samples will be found on every hand, and in all directions, and man, the greatest of all of nature's products, while imperfect in himself, is improving and adapting the things he sees about him. WHY SPECIALLY-DESIGNED FORMS IMPROVE NATURAL STRUCTURES.--The reason for this is, primarily, that the inventor must design the article for its special work, and in doing so makes it better adapted to do that particular thing. The hands and fingers can do a multiplicity of things, but it cannot do any particular work with the facility or the degree of perfection that is possible with the machine made for that purpose. The hands and fingers will bind a sheaf of wheat, but it cannot compete with the special machine made for that purpose. On the other hand the binder has no capacity to do anything else than what it was specially made for. In applying the same sort of reasoning to the building of flying machines we must be led to the conclusion that the inventor can, and will, eventually, bring out a form which is as far superior to the form which nature has taught us to use as the wonderful machines we see all about us are superior to carry out the special work they were designed to do. On land, man has shown this superiority over matter, and so on the sea. Singularly, the submarines, which go beneath the sea, are very far from that perfected state which have been attained by vessels sailing on the surface; and while the means of transportation on land are arriving at points where the developments are swift and remarkable, the space above the earth has not yet been conquered, but is going through that same period of development which precedes the production of the true form itself. MECHANISM DEVOID OF INTELLIGENCE.--The great error, however, in seeking to copy nature's form in a flying machine is, that we cannot invest the mechanism with that which the bird has, namely, a guiding intelligence to direct it instinctively, as the flying creature does. A MACHINE MUST HAVE A SUBSTITUTE FOR INTELLIGENCE. --Such being the case it must be endowed with something which is a substitute. A bird is a supple, pliant organism; a machine is a rigid structure. One is capable of being directed by a mind which is a part of the thing itself; while the other must depend on an intelligence which is separate from it, and not responsive in feeling or movement.