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CHAPTER VIII. 



ANALOGIES. 



ANALOGIES are not proofs, but they facilitate 

 the explanation of abstract ideas and theo- 

 retical processes, and with this object we 

 gladly avail ourselves of the developments 

 of the loom and of the steam-engine to illus- 

 trate our theory of the evolution of life. 



The Art of Weaving. 



The Jacquard loom may be described as 

 a mechanism that, when set in motion and 

 supplied with suitable material, will go on 

 weaving cloth of identically the same texture 

 and pattern, so long as the speed of the 

 machine, the material, and the conditions 

 remain unchanged. 



The forces 'of the loom are of two kinds : 

 one a " general " force the motive power ; 

 and the other a force specific to every web 

 of different pattern produces the particular 



