A very remarkable application of this principle offers itself to our contemplation, in the artificial memory which was invented by the ancient orators and rhetoricians. The orator made choice of a set of objects, sufficient in number to answer his purpose. The ideas of those objects he taught himself, by frequent repetition, to pass through his mind in one constant order. The objects which he chose were commonly such as aided him in fixing them according to a certain order in his memory; the parts, for example, of some public building, or other remarkable assemblage. Having so prepared himself, the mode in which he made use of his machinery was as follows. The topics or sentiments of his speech were {325} to follow in a certain order. The parts of the building he had chosen as his instrument had previously been taught to follow by association, in a certain order. With the first of these, then, he associated the first topic of his discourse; with the second, the second, and so on. The first part of the building suggested the first topic; the second, the second; and each another, to the end of his discourse.[89] [Bain's footnote 89: The conditions of the success of this expedient are interesting to study as illustrations of the working of association. The supposition is that the parts of the building are perfectly coherent in the mind, that they can recall each other easily and rapidly. The advantage gained will depend entirely upon the superior facility of attaching a head of discourse to the visible appearance of a room, as compared with the facility of attaching it to a previous head. If we can form an enduring bond between a topic and the picture of an interior, by a smaller mental effort than is necessary to conjoin two successive topics, there is a gain by the employment of the device; the difference of the two efforts is the measure of the gain. Probably the result would depend upon the relative force of the pictorial and the verbal memory in the individual mind. In minds where the pictorial element prevails, there might be a positive advantage; in cases where the pictorial power is feeble and the verbal power strong, there would almost certainly be a dead loss.--_B._]