ZOOLOGY OF GALAPAGOS ISLANDS. 161 



If, however, even in our limited command of this 

 giand element, we can detect such transitions as 

 those amongst the cerealia, or in a common in- 

 fusion, may we not well suppose that much greater 

 have taken place in the course of the vast series 

 of ages here described ? Absolute proof on such 

 a point may be impossible ; but nearly the same 

 effect may be reached, if we see vestiges of the 

 supposed facts in living phenomena, just as we 

 conclude upon the formation of stratified and 

 igneous rocks from seeing similar phenomena, 

 generally on a smaller scale, taking place before 

 our eyes. 



There is another mode of attaining the means 

 of a tolerably definite conclusion, where perfect 

 proof is unattainable. This is to show a portion 

 or fraction of the entire phenomenon, in conformity 

 with the hypothesis as to the whole. Now this can 

 be done ia the case under consideration. There 

 are isolated parts of the earth, which we know to 

 have become dry land more recently than others. 

 Such is the Galapagos group of islands, situated 

 in the Pacific, between five and six hundred miles 

 from the American coast. They are wholly of 

 volcanic origin, and are considered by Mr. Darwin 

 as ha\ing been raised out of the sea, " within a 



