THE CEREBRUM, AND ITS FUNCTIONS. 779 



natural juxtaposition, and thus to induce a routine which is often most un- 

 meaning ( 836), similarity breaks through juxtaposition, and brings together 

 like objects from all quarters. And it is further to be observed, that, with this 

 purely intellectual operation, there is frequently associated a peculiar feeling of 

 pleasure, which constitutes a true emotional state. All the discoveries of 

 identification, where use and wont are suddenly broken through, and a common 

 feature is made known among objects previously looked on as entirely different, 

 produce a flash of agreeable surprise, and the kind of sparkling cheerfulness 

 that arises from the sudden lightening of a burden. There are few who devote 

 themselves to the pursuit of Science, who do not experience this pleasure, either 

 from the detection of new relations of similarity by their own perception of them, 

 or in the recognition of them as developed by others. It is, however, much 

 more intense in some minds than in others; and according to its intensity, will 

 it act as a motive in the prosecution of scientific inquiry amidst discouragements 

 and difficulties. It is recorded of Newton, that when he was bringing his great 

 idea of the causative relation between terrestrial gravity and the motions of the 

 heavenly bodies to the test of calculation, his agitation became so great that 

 he could not complete the computation, and was obliged to request a friend to 

 do so. 



809. Although the single relations established between ideas, either through 

 contiguity or through similarity, may suffice for their mutual connection, yet 

 that connection becomes much stronger when two or more such relations exist 

 consentaneously. Thus, if there be present to our minds two states of con- 

 sciousness, each of them associated, either by contiguity or similarity, with some 

 third state that is past and " out of mind" at the time, the compound action is 

 more effective than either action would be separately ; that is, the separate sug- 

 gestions might be too weak to revive the past state of consciousness, but repro- 

 duce it by acting together. Of this, which has been termed the Law of 

 Compound Association, we have examples continually occurring to us in the 

 phenomena of Memory ; but it is especially brought into operation in the volun- 

 tary act of Recollection ( 818). Another mode in which the associative tend- 

 ency operates, is in the formation of aggregate conceptions of things that have 

 never been brought before our consciousness by sensory impressions. This 

 faculty, which has been termed that of Constructive Association, is the founda- 

 tion of Imagination ; and it is exercised in every other mental operation in 

 which we pass from the known to the unknown. When we attempt to form a 

 conception, which shall differ from one that we have already experienced as a 

 matter of objective reality, by the introduction of only a single new element 

 as when we imagine a brick building replaced by one of stone in every respect 

 similar as to size and form we substitute in our minds the idea of stone for 

 that of brick, and associate it by the principle of contiguity with those other 

 ideas, of which that of the whole building is an aggregate. So, again, if we 

 conceive a known building transferred from its actual site to some other already 

 known to us, we dissociate the existing combinations, and keep together the 

 ideas which were previously separated, until their contiguity has so intimately 

 united them, that the picture of the supposed combination may present itself to 

 the mind exactly as if it had been a real scene which we had long and familiarly 

 known. By a further extension of the same power, we may conceive the ele- 

 ments to be varied, as well as the mode of their combination ; and thus we may 

 bring before our consciousness a representation, in which no particular has ever 

 been before our minds under any similar aspect, and which is, therefore, as a 

 ivholc, entirely new to us, notwithstanding that, when we decompose it into its 

 ultimate elements, we shall find that each of these has been previously before 

 our consciousness. Such a representation, by being continually dwelt on, may 

 come to have all the force and vividness of one derived from an actual sensory 



