Association by Contiguity manifests particularly in the processes of memory. In its two phases of (1) Contiguity of Time; and (2) Contiguity of Space, respectively, it brings together before the field of consciousness ideas associated with each by reason of their time or space relations. Thus, if we remember a certain thing, we find it easy to remember things which occurred immediately before, or immediately after that particular thing. Verbal memory depends largely upon the contiguity of time, as for instance, our ability to repeat a poem, or passage from a book, if we can recall the first words thereof. Children often possess this form of memory to a surprising degree; and adults with only a limited degree of understanding may repeat freely long extracts from speeches they have heard, or even arbitrary jumbles of words. Visual memory depends largely upon contiguity of space, as for instance our ability to recall the details of scenes, when starting from a given point. In both of these forms of association by contiguity the mental operation is akin to that of unwinding a ball of yarn, the ideas, thus associated in the sequence of time or place, following each other into the field of consciousness. Association by Contiguity, while important in itself, properly belongs to the general subject of Memory, and as we have considered it in the volume of this series devoted to the last mentioned subject, we shall not speak of it further here. Association by Similarity, however, possesses a special interest to students of the particular subject of the culture of the Understanding. If we were compelled to rely upon the association of contiguity for our understanding of things, we would understand a thing merely in its relations to that which went before or came after it; or by the things which were near it in space--we would have to unwind the mental ball of time and space relations in order to bring into consciousness the associated relations of anything. The Association of Similarity, however, remedies this defect, and gives us a higher and broader association. Speaking of Association of Similarity, Kay says: "It is of the utmost importance to us in forming a judgment of things, or in determining upon a particular line of conduct, to be able to bring together before the mind a number of instances of a _similar_ kind, recent or long past, which may aid us in coming to a right determination. Thus, we may judge of the nature or quality of an article, and obtain light and leading in regard to any subject that may be before us. In this way we arrange and classify and reason by induction. _This is known as rational or philosophical association._"