158 EDITORIAL 



on to greater depression, the volume of the hydrosphere meanwhile 

 increasing and assisting in the submersion. The portions now 

 submerged were presumably affected by reliefs not unlike those of 

 the continental portions at like stages of evolution. In the course 

 of their gradual submersion, the more protuberant swells and ridges 

 are presumed to have stood forth from the growing seas as variously 

 shaped lands which doubtless had a dominant tendency to elongated 

 swells of ridge-like aspect, such as now affect the ocean bottoms and 

 are being brought out more and more as soundings multiply. Not 

 that all are necessarily of this class, however. In the slow process 

 of their submergence, these swells and ridges were doubtless subject 

 to denudation and circum-decomposition, as are other lands, and 

 hence are similarly attended by sedimentary rocks. Some of these 

 may have been submerged only in the later deformations of the 

 earth's body, those of the Tertiary period perhaps, and previous 

 to this they may have constituted bridges between the continents, 

 and thus have satisfied the requirements of biological data, if these 

 are indeed requirements. The loss, through deformation, of such 

 bridge-connections of comparatively limited area and of moderate 

 depression makes a relatively small demand on dynamic agencies and 

 involves the withdrawal of a relatively small volume of water from the 

 continental platforms. On the other hand, if vast continents be sup- 

 posed to have arisen from the depths of the Atlantic, Pacific, and 

 Indian Oceans, and to have again subsided, not only is a heavy tax 

 laid on dynamic resources, but great volumes of displaced water must 

 be accounted for in a complete hypothesis. We can no longer leave 

 these considerations out of account as in the past, for the days of 

 legitimate appeal to terrae incognitae are over. 



If the hypothesis of a relatively thin shell shearing over a solid 

 substratum, which seems to be forced upon us by a study of the 

 folds of the corrugated mountains, be entertained,^ the occurrence 

 of foliated rocks at shallow depths beneath the oceans, as well as 

 the continents, is to be assumed, though perhaps their extent and 

 degree of development may be inferior. These foliated rocks may 

 have as wide a range of lithological characters as the igneous rocks 

 of the sub-oceanic crust which, as we have seen before, under the 



I Chamberlin and Salisbury, loc. cit., pp. 125-32. 



