NATURAL SCIENCE IN THE NINETEENTH CENTURY 389 



family relationship through a common ancestry, weighed heavily 

 against the theory of special and separate creation by an ex- 

 traneous will in remote time, with no provision for change to meet 

 changing conditions. 



THE SCALE OF LIFE AND THE PHASES OF LIFE. It had often 

 been commented upon that in the world of life there is always 

 present and requiring explanation what Bonnet called the " scale 

 of life," i.e. the fact that plants and animals not only differ greatly 

 in structure and complexity, but that both may be arranged in a 

 kind of ascending or descending natural scale (ladder) with highly 

 complex forms at the top and relatively simple ones at the bot- 

 tom. On the doctrine of special creation it was difficult to find 

 any reason for or advantage in the existence of such a scale, 

 while the suggestion was obvious that the higher forms had 

 somehow come from or passed through lower forms. A rapid 

 modification of living forms, such as this suggestion required, is 

 obvious in everyday life being exemplified by the so-called phases of 

 life, in which infancy makes way for youth, youth for maturity, 

 and maturity for age. To the attentive observer living matter 

 appears to be thus forever changing, and on the whole progressing 

 or advancing from simplicity to complexity. 



In this respect the stellar universe at first sight appears very 

 different, for here permanence rather than change seems to pre- 

 vail. As for the earth, changes, indeed, do often occur and some- 

 times progressively, as in erosion, glacial action, and the work of the 

 tides, so that the earth seems to stand in this respect somewhere 

 between changing and advancing organic life and the unchanging 

 heavens. When, therefore, the idea broached by Hutton and 

 Smith at the end of the eighteenth century that the surface of the 

 earth has been made and is still being made what it is to-day, not 

 suddenly and once for all by special creation centuries ago, but 

 gradually, and by forces and processes similar to those now acting, 

 a new and revolutionary notion of the genesis of the earth's crust 

 arose, and one contrary to the idea of special creation. The same 

 idea carried further and developed by Lyell in 1830 became thence- 

 forward all important : 



