54 PICTURESQUE SKETCHES 



being quite enough to produce, at the present clay, a 

 marked difference in the appearance of the group of 

 inhabitants of adjacent districts, which difference is 

 perfectly appreciable at the first glance by one accus- 

 tomed to observe with any degree of accuracy. 



The general nature of the animal remains is not 

 the only means possessed by the Naturalist, or made 

 use of by the Geologist, to determine the circum- 

 stances under which submarine deposits may have 

 taken place. There is now a chain of observations 

 extending over the whole series of known strata ; 

 and, regard being had to the present advanced state 

 of knowledge of the existing species of animals, it has 

 been distinctly proved, that the more carefully and 

 strictly these observations are compared and brought 

 to bear upon one another, the more manifest is it, that, 

 ever since the first introduction of animals upon earth, 

 there have been successive creations of species similar 

 to one another, but not identical, -performing often 

 the same office, but perfectly distinguishable, and in- 

 volving a constant introduction of new species, al- 

 though never, not even in a single instance, involving 

 the repetition of a species that has once died out. 



The statement of this fact, namely, that species, 

 like individuals, have a certain limited term of exist- 

 ence, has already been made indirectly in the preced- 

 ing chapter ; and I have there described a number of 

 animals very much unlike any that now exist, although 

 not without such resemblances as indicate the posses- 

 sion of analogous habits, and exhibit proof of unity of 

 design running through creation, and connecting even 

 the most ancient species with those yet surviving ; but 

 I did not there speak concerning that peculiar sue- 



