In the classification of the Sciences, the first and most important distinction is between the fundamental sciences, sometimes called the Abstract sciences, and the derivative or Concrete branches. My purpose does not require any nice clearing of the meanings of those technical terms. It is sufficient to say that the fundamental sciences are those that embrace distinct departments of the natural forces or phenomena; and the derivative or concrete departments assume all the laws laid down in the others, and apply them in certain spheres of natural objects. For example, Chemistry is a primary, fundamental, or abstract science; and Mineralogy is a derivative and concrete science. In Chemistry the stress lies in explaining a peculiar kind of force, called chemical force; in Mineralogy the stress is laid on the description and classification of a select group of natural objects. The fundamental, or departmental sciences, as most commonly accepted, are these:--1. Mathematics; 2. Natural Philosophy, or Physics; 3. Chemistry; 4. Biology; 5. Psychology. They may be, therefore, expressed as Formal, Inanimate, Animate, and Mental. In these sciences, the idea is to view exhaustively some department of natural phenomena, and to assume the order best suited for the elucidation of the phenomena. Mathematics, the Formal Science, exhausts the relations of Quantity and Number; measure being a universal property of things. Natural Philosophy, in its two divisions (molar and molecular), deals with one kind of force; Chemistry with another: and the two together conspire to exhaust the phenomena of _inanimate_ nature; being indispensably aided by the laws and formulae of quantity, as given in Mathematics. Biology turns over a new leaf; it takes up the phenomenon--Life, or the _animated_ world. Finally, Psychology makes another stride, and embraces the sphere of _mind_. Now, there is no fact or phenomenon of the world that is not comprised under the doctrines expounded in some one or other of these sciences. We may have fifty "ologies" besides, but they will merely repeat for special ends, or in special connections, the principles already comprised in these five fundamental subjects. The regular, systematic, exhaustive account of the laws of nature is to be found within their compass. [ORDER OF THE FUNDAMENTAL SCIENCES.]