486 MECHANICAL ILLUSTKATION OF CRISES. 



the conclusion thereof, the hypothesis to which he had thus hastened 

 would be confirmed. True to the time, the bell would again strike, but, 

 instead of striking only once, it would strike twice. Admonished of the 

 hastiness of his hypothesis, our philosopher might now be induced to 

 pause before he generalized again, and, after watching through 3600 more 

 beats, the clock would strike thrice. 



Now, surely, he would feel absolutely certain of having reached the 

 tfde interpretation of the action of the machine at last. His third and 

 corrected conclusion would be that each group of 3600 beats was register- 

 ed by the bell, the number of strokes upon which indicated the number 

 of such groups, and that this it would do continuously. 



Patiently listening through many thousand beats, he would find that 

 every thing confirmed his new and improved induction. He would hear, 

 in their regular succession, ten, eleven, and twelve strokes made by the 

 clock. Of course, his expectation would now be confirmed that at the 

 next time the clock struck it would be thirteen. How great would be 

 his surprise to find it was only one ! 



Perseveringly continuing his examination, he would reach, at last, the 

 true law regulating the indications of the machine, and would find that 

 the partial conclusions to which he had successively arrived, and which 

 he had thought, at the time, to be substantiated by a superfluity of facts, 

 were in themselves incomplete, and in that respect erroneous ; but he 

 would also observe that whatever truth there was in them was embraced 

 in the final induction that the machine was not as simple as he had at 

 first supposed, and that the critical variations which in succession had 

 surprised him were all embraced in the original plan of its construction. 

 Our imaginary philosopher has passed through a mental exercise precise- 

 ly like that which is befalling modern comparative physiologists. From 

 his labors, disappointments, and eventual success, they may gather en- 

 couragement. The clock of the universe does not forever go on vibrat- 

 ing monotonously. A thousand years upon it are only as the beat of a 

 pendulum ; but it, too, has its periods of critical variation variations that 

 were included in its original device. 



The point which I wish to impress by these illustrations is, that there 

 A lication of * s a definite career which an organism must follow, accord- 

 the preceding ing to its exposure to existing physical conditions, and that, 

 lon< though this career may seem to be continuous, it by no means 

 follows that it shall not exhibit an instantaneous and critical change, and 

 that, on a sudden, the organism may assume a specifically new aspect ; 

 and though, in what has thus far been said, reference has been had chief- 

 Influence of ly to plants, these observations all apply, in like manner, to 

 ainma l s - I do not propose, however, to enter on that branch 

 of the inquiry now, but, as an illustration of the influence of 



