IV. Its adaptability to artificial culture. A. The ease with which it may be grown. B. Its value as a food. V. Localities suitable for its culture. A. The kind of soil which should underlie the ponds. B. The character of the water supply. VI. The method of culture. A. The size and construction of the ponds. 2. In "class," or triple-pond culture. b. The breeding pond. c. The culture, or regular pond. B. Stocking the ponds and the care of the fish. 1. In "class" culture. 2. In "mixed" culture. C. Marketing the grown fish. VII. The extent and importance of the carp industry. A. In Europe. B. In the United States. In this outline it will be observed that the various headings and sub-headings are phrases only. This is what is known as the topical outline. It is sometimes desirable, however,-especially where the outline is to be read by others besides the writer,-to have the main headings complete sentences, and the sub-headings either complete sentences or phrases complementary to the headings under which they are placed. This gives greater definiteness to an outline, and indicates more precisely the writer's point of view. The following, slightly adapted from a student's theme, will illustrate the method: THE DISSEMINATION OF THE SEEDS OF WILD PLANTS I. Introduction: A natural means of disseminating the seeds of wild plants is necessary to prevent many species becoming extinct. II. The chief natural agencies which disseminate the seeds of wild plants are: A. The wind, which distributes 1. Light seeds having plumes or wing-like attachments, such as those of a. The Canada thistle. b. The maple. 2. Seeds of plants which, after they mature and die, may be rolled along over level plains, such as a. Tickle-grass. b. Tumble-weed. B. The waters of rivers, lakes, etc., which carry the seeds of such plants as 1. The water-lily. 2. The willow. C. Animals, which transport seeds 1. By devouring the fruits of such plants as a. The blackberry. b. The cherry. 2. By carrying in their fur or hair the barbed seed pods of such plants as a. The burdock. b. The cockle-bur. D. The explosive action of certain seed pods, which by violently ejecting the seeds scatters them widely; for example, 1. The violet. 2. The witch-hazel. 3. EXPOSITION WHICH AIMS TO DEFINE OR TO CLASSIFY The typical moods of exposition are definition and classification. That is to say, in exposition we are, for the most part, either trying to make clear what something is, or, on the other hand, trying to group things in classes in accordance with their natural relationships. In trying to make clear what a thing is, we are, of course, trying to indicate what its essential characteristics, attributes, or qualities are. Exposition by definition may therefore be defined as the setting forth of the essential characteristics of something; it is the determining of the meaning or content of a general idea. The nucleus of an expository composition of the defining kind is what is known as the logical definition. This differs from the ordinary or loose definition simply in being more formal and exact. Its aim is to mark out the limits or boundaries of the term to be defined, to differentiate it from all other terms of similar meaning, so that the things for which it stands may be distinguished from all other things which can be put in the same general class. Thus if we wish to give a logical definition of the term " parallelogram, we must so frame our definition that the difference between a parallelogram and all other plane fig ures is exactly indicated. This involves the regarding of the term to be defined as representing a species, the bringing of that species within a higher class or genus, and the enumerating of the essential qualities or attributes which distinguish the species from the genus. These distinguishing qualities or attributes are usually called the differentia. The following examples will illustrate the form in which the logical definition usually occurs: In testing the validity of a definition, we have to take into account both the content and the form. With regard to the content, the main question is whether the differentia be satisfactory or not. In a valid definition, the differentia must always be (1) an essential characteristic of the species or thing for which the term to be defined stands, and (2) a characteristic not possessed by any other member of the genus. Thus if we were to define a bird as an animal capable of flying," the definition would be faulty, since, in the first place, not all birds are capable of flying, and, in the second place, other animals than birds-bats, for instance-possess this characteristic. That is to say, the differentia would not be an essential attribute of birds; nor would it be an attribute possessed by no other animals than birds. The definition would thus be, at one point, too narrow and at another, too broad; it would not cover all the territory indicated by the term to be defined, yet it would stretch beyond that territory. In other words, it would admit of exceptions, and a logical definition must be true universally, else it is worthless. It should be noted that accuracy of definition does not necessarily imply that the differentia must exhaust all the characteristics which distinguish the species from the genus. In exact scientific definitions, accuracy of this kind may be desirable, but it is not necessary in those of a more literary kind. For example, in the definition of man as " a reasoning animal," the differentia," reasoning," does not cover all the qualities distinguishing man from other animals; but the definition is a perfectly valid one for all that. It is accurate as far as it goes. It is thus often possible, especially in popular exposition, where absolute exactness is seldom an essential point, for a writer to have a good deal of freedom with regard to the choice of differentia for his definition. "Man is a reasoning animal" might be a perfectly good definition for one purpose; but for another, man is a worshipping animal" might be better. Neither of these defini |