I am actually weary of telling people that I do not pretend to adduce direct evidence of one species changing into another, but that I believe that this view in the main is correct, because so many phenomena can be thus grouped together and explained.

But it is generally of no use; I cannot make persons see this.

I generally throw in their teeth the universally admitted theory of the undulation of light,--neither the undulation nor the very existence of ether being proved, yet admitted because the view explains so much.

You are one of the very few who have seen this, and have now put it most forcibly and clearly.

I am much pleased to see how carefully you have read my book, and, what is far more important, reflected on so many points with an independent spirit.