194 GEOLOGICAL DISTRIBUTION. 



reasonable to expect that, in some of the regions here indicated, 

 the connections will be found that elsewhere are wanting. But, 

 even granting the justice of this plea, the facts, such as they are, are 

 of themselves sufficiently remarkable, as indicating how very far- 

 reaching in their action must have been the forces that were directly 

 concerned in the causation of breaks. It is a little difficult to con- 

 ceive of secular elevations and depressions of the land-surface ex- 

 tending simultaneously over nearly the entire circumference of the 

 earth, even in the restricted area of the Temperate Zone ; but such 

 must undoubtedly have been the case to account for the phenomena 

 that are presented to us. Otherwise complete passage-beds would 

 be of much more frequent occurrence than we know them to be. 

 This does not preclude the possibility of the existence of local areas 

 showing a differential or contrary movement ; such, however, do not 

 seem to have in any way interfered with the grand scheme that was 

 involved. But it is very unlikely that elevation or subsidence either 

 was, or could be, universal at any given period ; on the contrary, it 

 appears far more rational to suppose that every very extensive eleva- 

 tion was accompanied by a corresponding depression somewhere 

 else, and vice versa, and thus some sort of balance maintained. If 

 this is so, then we would naturally look in some distant quarter for 

 the counterpart of the effects which either elevation or subsidence * 

 may have produced in any one region of the globe. Seeing how- 

 very general throughout the vast expanse of the Northern Hemi- 

 sphere are certain breaks in the geological series, are we not justi- 

 fied in looking to the region farther south for the evidences prov- 

 ing uninterrupted sedimentation and continuous organic evolu- 

 tion ? 



If we attach full weight to the imperfection of the geological 

 record, it is not difficult to account for the apparent abrupt ap- 

 pearance of certain animal groups or faunas ; indeed, the problem 

 would have been far more difficult to solve had the case been other- 

 wise. But there is one special instance of such appearance which 

 is not so readily accounted for, and which, under any hypothesis, 

 is almost inexplicable. We refer to the sudden appearance of the 

 numerous forms of life which characterise the oldest fossiliferous 

 formation with which we are at present acquainted, the Cambrian, 



* Reference is here made to the more extensive movements of the crust, 

 producing the profounder breaks. 



