602 PSYCHOLOGY. 



must conspire with the intellectual energy of resuscitation by similars, 

 in order to summon together in the view three structures so different. 

 We can see, by an instance like this, how new adaptations of existing 

 machinery might arise in the mind of a mechanical inventor. When it 

 first occurred to a reflecting mind that moving water had a property 

 identical with human or brute force, namely, the property ot setting 

 other masses in motion, overcoming inertia and resistance, — when the 

 sight of the stream suggested through this point of likeness the power 

 of the animal, — a new addition was made to the class of prime movers, 

 and when circumstances permitted, this power could become a substi- 

 tute for the others. It may seem to the modern understanding, famil- 

 iar with water-wheels and drifting rafts, that the similarity here was an 

 extremely obvious one. But if we put ourselves back into an early 

 state of mind, when running water affected the mind by its brilliancy, 

 its roar, and irregular devastation, we may easily suppose that to iden- 

 tify this with animal muscular energy was by no means an obvious 

 effect. Doubtless when a mind arose, insensible by natural constitution 

 to the superficial aspects of things, and having withal a great stretch of 

 identifying intellect, such a comparison would then be possible. W& 

 may pursue the same example one stage further, and come to the dis- 

 covery of steam power, or the identification of expanding vapor with 

 the previously known sources of mechanical force. To the common eye, 

 for ages, vapor presented itself as clouds in the sky; or as a hissing 

 noise at the spout of a kettle, with the formation of a foggy curling 

 cloud at a few inches' distance. The forcing up of the lid of a kettle 

 may also have been occasionally ob.served. But how long was it ere 

 any one was struck with the parallelism of this appearance with a blast 

 of wind, a rush of water, or an exertion of animal muscle ? The dis- 

 cordance was too great tobe broken through by such a faint and limited 

 amount of likeness. In one mind, however, the identification did take 

 place, and was followed out into its consequences. The likeness had 

 occurred to other minds previously, but not with the same results. 

 Such minds must have been in some way or other distinguished above 

 the millions of mankind; and we are now endeavoring to give the ex- 

 planation of their superiority. The intellectual character of Watt con- 

 tained all the elements preparatory to a great stroke of similarity in 

 such a case; — a high susceptibility, both by nature and by education, 

 to the mechanical properties of bodies; ample previous knowledge or 

 familiarity; and indifference to the superficial and sensational effects 

 of things. It is not only possible, however, but exceednigly probable, 

 that many men possessed all these accomplishments; they are of a kind 

 not transcending common abilities. They would in some degree attach 

 to a mechanical education almost as a matter of course. That the dis- 

 covery was not sooner made supposes that something farther, and not 

 of common occurrence, was necessary; and this additional endowment; 

 appears to be the identifying power of Similarity in general; the ten- 

 dency to detect likeness in the midst of disparity and disguise. This 



