Machine and its Model. 271 



Every instrument, whether it be used for the generation or for 

 the transference of power, has a best size and a best form. The 

 contemplation of the whole animal and vegetable kingdoms teaches 

 this truth. Each species of animal attains to a determinate size, 

 beyond which it seldom proceeds, and short of which it seldoms 

 stops, unless man has interfered with the regular course of nature, 

 and deranged, as his contrivnaces too often do, that determinate, 

 succession of events which is conspicuous in the history of each tribe 

 of what we are pleased to call the lower animals. Each animal 

 and each vegetable, in its progress from infancy to maturity, assumes, at 

 each stage of that progress, such a form as best assorts with the con- 

 solidation of its parts, and with the mode of its living. The wisdom 

 and the benificence of this arrangement, and the skilfulness with 

 which it is made, become the more apparent when we carry our 

 contemplation beyond the globe which we inhabit to those other worlds 

 which circulate round the same sun. Were man, in his present state, 

 and with his present powers, planted on the surface of Jupiter, he 

 would be crushed beneath his own weight : and if, on the surface 

 of that planet, there do exist beings of the same structure and of 

 the same material as man, one of us would be a Man-mountain 

 among them. If, on the other hand, we were transported to the 

 surface of the Moon, or of one of the Asteroids, our strength would 

 fit us for progressing rather in the manner of the grasshopper than 

 of the man : bipeds, living and moving as we do, would there realize 

 the counter-vision of Gulliver. 



The sizes, then, of the objects which, on the surface of this earth, 

 surround us, are not fixed by chance, but determined by the im- 

 mutable laws of nature ', and, in every case. Nature has pushed her 

 exertions to the utmost. There is a limit, both ways, to the size 

 of quadrupeds ; there is a limit, both ways, to the size of birds ; 

 and, although myriads of insects may be as yet unknown, I hesitate 

 not to affirm that, among these also, we have the double limit. 

 These are not mere speculative truths ; they teach us this useful and 

 needful lesson, that there are bounds beyond which no ingenuity can 

 carry us, and toward vi^hich we can only hope to approach. How often 

 have men attempted to plume themselves with wings? How many 

 years were spent in search of the golden secret ? How many for- 

 tunes have been wasted in the contrivance of perpetual motions ! 

 And, to come nearer the present moment, how many have ruined 

 themselves with the locomotive engine ! This last is the bubble of 

 the present day, and on it I shall make a few observations. 



