Now here we have a distinct body of phenomena or facts, all based upon a single central Idea or Quality — Exchange ability; and, therefore, it is fitted to form a great Demonstrative Science of the same rank as Mechanics or Optics, or any other Physical Science. Another great body of particular facts is won from the vague ?oating mass of human knowledge — won from the void and formless infinite — and circumscribed by a definition, and formed into a great Inductive Science, whose investigations must be governed by the same general principles of Inductive Logic as all other sciences are and yet it will be found to contribute its own quota to Inductive Logic — bearing a general similarity to its sister sciences, and yet with peculiarities of its own.