298 Doubts Relative to the Epochal and 



Didymus," which tract has a very direct bearing upon the 

 whole subject. 



The entire evidence of a succession of changes and con- 

 vulsions of the earth, or only one mighty and exhaustive 

 one, turns upon the subject of rock formation from detritus, 

 and this paper will conclude the present short treatise on 

 vital force, and is, as it were, a kind of corollary to the 

 entire subject of epidemics. 



DOUBTS RELATIVE TO THE EPOCHAL AND DETRITAL 

 THEORY OF GEOLOGY. 



As epochs or eras in geological language are not accepted 

 as representing the exact opinions held by most geologists 

 at the present time, and any attempt to disprove the epochal 

 or detrital theory of geology, based upon the notion that 

 every stratum has been formed at a particular period of 

 time, and that during the same period of time none other has 

 been in process of formation at some distant portion of 

 the globe, is totally unnecessary ; since most geologists are 

 prepared to admit that upon distant areas of the earth's 

 surface, in one part a given stratum may be completed, 

 whilst at another part a new stratum is in process of 

 formation. Thus free scope is left for the application of 

 the developmental theory of Darwin, upon the basis of 

 natural selection, without the necessity of supposing each 

 new species requiring a special act of creative power for 

 its manifestation, but only an improved condition favourable 

 for its development. 



