vii CREATION BY LAW 149 



the growth of this one species of plant as to cause its nectary 

 to increase to this enormous length ; and at the same time, 

 by an equally special act, determined the flow of nourishment 

 in the organisation of the moth, so as to cause its proboscis to 

 increase in exactly the same proportion, having previously so 

 constructed the Angrsecum that it could only be maintained 

 in existence by the agency of this moth. But what proof is 

 given or suggested that this was the mode by which the ad- 

 justment took place ? None whatever, except a feeling that 

 there is an adjustment of a delicate kind, and an inability to 

 see how known causes could have produced such an adjust- 

 ment. I believe I have shown, however, that such an 

 adjustment is not only possible but inevitable, unless at some 

 point or other we deny the action of those simple laws which 

 we have already admitted to be but the expressions of exist- 

 ing facts. 



Adaptation brought about by General Laws 



It is difficult to find anything like parallel cases in inorganic 

 nature, but that of a river may perhaps illustrate the subject 

 in some degree. Let us suppose a person totally ignorant of 

 modern geology to study carefully a great river system. He 

 finds in its lower part a deep broad channel filled to the 

 brim, flowing slowly through a flat country and carrying out 

 to the sea a quantity of fine sediment. Higher up it branches 

 into a number of smaller channels, flowing alternately through 

 flat valleys and between high banks ; sometimes he finds a 

 deep rocky bed with perpendicular walls, carrying the water 

 through a chain of hills ; where the stream is narrow he finds 

 it deep, where wide shallow. Farther up still, he comes to a 

 mountainous region, with hundreds of streams and rivulets, 

 each with its tributary rills and gullies, collecting the water 

 from every square mile of surface, and every channel adapted 

 to the water that it has to carry. He finds that the bed of 

 every branch and stream and rivulet has a steeper and 

 steeper slope as it approaches its sources, and is thus enabled 

 to carry off the water from heavy rains, and to bear away 

 the stones and pebbles and gravel that would otherwise block 

 up its course. In every part of this system he would see 

 exact adaptation of means to an end. He would say that 

 this system of channels must have been designed, it answers 



