136 LECTURES ON EVOLUTION in 



desire to know is, is it a fact that evolution 

 took place ? As to the amount of time which 

 evolution may have occupied, we are in the 

 hands of the physicist and the astronomer, whose 

 business it is to deal with those questions. 



I have now, ladies and gentlemen, arrived at 

 the conclusion of the task which I set before 

 myself when I undertook to deliver these lectures. 

 My purpose has been, not to enable those among 

 you who have paid no attention to these subjects 

 before, to leave this room in a condition to decide 

 upon the validity or the invalidity of the hypo- 

 thesis of evolution ; but I have desired to put 

 before you the principles upon which all hypo- 

 theses respecting the history of Nature must be 

 judged ; and furthermore, to make apparent the 

 nature of the evidence and the amount of cogency 

 which is to be expected and may be obtained 

 from it. To this end, I have not hesitated to 

 regard you as genuine students and persons de- 

 sirous of knowing the truth. I have not shrunk 

 from taking you through long discussions, that 

 I fear may have sometimes tried your patience; 

 and I have inflicted upon you details which 

 were indispensable, but which may well have 

 been wearisome. But I shall rejoice I shall 

 consider that I have done you the greatest ser- 

 vice which it was in my power to do if I have 

 thus convinced you that the great question which 



