ANALOGIES. 3 7 



A new combination is necessary only to 

 differentiate the centre patterns ; the forces 

 that wove the first cloth are used for the 

 second, so far as they will subserve the 

 new design. 



And so in the evolution of life, the Specific 

 life-force of the antecessor was utilised in 

 evolving its successor, so far as it would 

 subserve that purpose. 



The Steam-engine. 



The steam-engines of the present day, 

 Parson's turbine excepted, have been evolved 

 from the Cornish pumping-engine of a cen- 

 tury past. The evolution has been by 

 numberless steps some insignificant, others 

 might be called gigantic ; but, small or large, 

 each was the result of an application of man's 

 intelligence and skill to the improvement of 

 an existing machine ; and each successive step 

 may be discovered by a comparative study of 

 the engines successively constructed. 



Steam-engines vary greatly in character 

 and appearance, but as the naturalist 

 classifies animals, so an expert engineer 

 could classify steam-engines into families, 

 genera, species, and varieties ; each as 

 clearly defined to the professional eye as 



