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vii CREATION BY LAW 149the growth of this one species of plant as to cause its nectaryto increase to this enormous length ;and at the same time,by an equally special act, determined the flow of nourishmentin the organisation of the moth, so as to cause its proboscis toincrease in exactly the same proportion, having previously soconstructed the Angrsecum that it could only be maintainedin existence by the agency of this moth. But what proof isgiven or suggested that this was the mode by which the adjustmenttook place None ? whatever, except a feeling thatthere is an adjustment of a delicate kind, and an inability tosee how known causes could have produced such an adjustment.I believe I have shown, however, that such anadjustment is not only possible but inevitable, unless at somepoint or other we deny the action of those simple laws whichwe have already admitted to be but the expressions of existingfacts.Adaptation brought about by General LawsIt is difficult to find anything like parallel cases in inorganicnature, but that of a river may perhaps illustrate the subjectin some degree. Let us suppose a person totally ignorant ofmodern geology to study carefully a great river system. Hefinds in its lower part a deep broad channel filled to thebrim, flowing slowly through a flat country and carrying outto the sea a quantity of fine sediment. Higher upit branchesinto a number of smaller channels, flowing alternately throughflat valleys and between high banks sometimes he finds a;deep rocky bed with perpendicular walls, carrying the waterthrough a chain of hills where the stream is narrow he finds; it deep, where wide shallow. Farther up still, he comes to amountainous region, with hundreds of streams and rivulets,each with its tributary rills and gullies, collecting the waterfrom every square mile of surface, and every channel adaptedto the water that it has to carry.He finds that the bed ofevery branch and stream and rivulet has a steeper andsteeper slope as it approaches its sources, and is thus enabledto carry off the water from heavy rains, and to bear awaythe stones and pebbles and gravelthat would otherwise blockup its course. In every part of this system he would seeexact adaptationof means to an end. He would say thatthis system of channels must have been itdesigned,answers