which the logic of that theory demands, you make transmu 
tation of species by geographical distribution impossible. 
But the theory which renders an acknowledged fact im 
possible ought surely to be discarded. 
(b) GEOLOGICAL CHANGES. 
“ O heaven ! that one might read the book of fate, 
And see the revolution of the times 
Make mountains level, and the continent 
(Weary of solid firmness) melt itself 
Into the sea ! and other times to see 
The beachy girdle of the ocean 
Too wide for Neptune’s hips.” 
—King Henry IV. Pari 2. Act Hi., sc. 1. 
The present habitat of the existing fauna and flora of 
the earth is due either to geographical distribution, or to 
a continuity of life in the same region during periods of 
geological transformation. Of such physical changes we 
have ample proofs in the strata of the earth’s crust. Moun 
tains bear traces of the fact that they have emerged from 
the sea. Tracts now covered with the sea were once dry 
land. The coal beneath our feet is an evidence that a 
tropical heat was once present in places which are now 
in the temperate zone, and evidence is not wanting of a 
vigorous vegetation in regions which are now arctic. And 
besides these great transformations of the outward scenes, 
there were also more gradual ones which introduced 
conditions so novel, that it was necessary that races of 
animals should be modified, if they were to continue to 
remain in the same locality. 
Much that has been said against the transmutation 
of species by means of Natural Selection, in the last