vir 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 Angraecum 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 
Tt 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 
