THE LOVE OF MOUNTAINS 229 



ing to pressure, others of rather different construction 

 rose and fell according to the intensity of the sunlight, 

 the present doctrine of barometric changes would be 

 destroyed. The barometer is, so to speak, actuated 

 by a single string. But plants and animals are things 

 of complex behaviour ; they are actuated by many 

 strings, and we never know when we have found them 

 all out. This is, I imagine, why what I have called 

 " negative exceptions " prove little or nothing in 

 Biology. You find that pulling a particular string 

 produces a certain action upon A. But B has no such 

 string, though you can give no good reason why it has 

 not Rare indeed are the cases in which we can 

 reason out a direct test, by which our biological 

 speculations are to stand or fall. Complexity, un- 

 fathomable complexity, on the part of Nature, and 

 ignorance on our side, preclude decisive experiments. 

 But in a humble way we may observe, and speculate, 

 and try. We shall not get the certainty of physical 

 demonstration, but we may hope in time to become 

 reasonably sure of interpretations more directly in- 

 teresting to mankind than any other conclusions of 

 Science more interesting because they bear so 

 immediately upon the great and mysterious problems 

 of Life. 



THE LOVE OF MOUNTAINS. 



August i. Simon's Seat, between Barden and 

 Pately Bridge, is one of the chief hills in this part of 

 the country, rising to near 1,600 feet above sea-level. 

 I have been to the top, to look once more at the 



