CHAP. XV.] OF CONTINENTS AND OCEANS. 335 



proving the present to be only a continuation of the Cre- 

 taceous period, I hold to be as untrue as the opinion that 

 the Chalk is not the product of a Cretaceous ocean. So 

 also with the arguments of those who urge and those who 

 oppose the doctrine of Uniformity in the rate of geologic 

 change ; the Unif ormitarian may push his advocacy to 

 such an extreme that he departs almost as far from the 

 truth in one direction as the Convulsionist does in another. 

 Avoiding these extremes, we may believe in the long- 

 continued existence of continents and oceans, and yet 

 admit that the Chalk is a genuine oceanic deposit ; we 

 may adopt the doctrine of Uniformity as our guiding 

 principle in the interpretation of the past, and yet believe 

 in the theory of Evolution. 



