Mountain Ranges and Submarine Ridges. 139 



and consequently as the primary cause of the various phenomena 

 which are observed in connection with geological formations, 

 such as stratification, cleavage, metamorphosis, and the final 

 melting and eruption of strata in the form of fluid or semi-fluid 

 matter. 



We have seen that the deposits found at the bottom of the 

 sea are different in their composition, according to the distance 

 and the depth at which they are laid down. We may therefore 

 expect that they will be affected differently by the heat 

 developed under the pressure of the superincumbent ocean. 

 If we attribute to pressure the observed increase of about 

 i° C. for every 20 fathoms in sub-aerial strata, we may expect 

 a much greater rate of increase in strata subject to the 

 enormous pressure of the ocean, and we may conceive the 

 possibility of the existence of strata in a fluid or semi-fluid 

 form at various depths below the bottom of the sea. The 

 earth's crust would in that case be composed of strata of 

 different degrees of solidity or fluidity, and the matter of the 

 more fluid strata would, under the continuous influence of 

 pressure, have a tendency to escape in a lateral direction. Now 

 this lateral pressure will manifest itself at the point of least 

 resistance — namely, upon the limit of an oceanic basin 

 where the vertical pressure of the superincumbent ocean ceases 

 altogether, or is sufficiently reduced to give way to the lateral 

 pressure. The result will be an upheaval of the overlying strata 

 along the margin of the. oceanic basin or along the axis of a 

 submarine plateau, and the formation of a mountain range or of 

 a submarine ridge, both of which may or may not assume the 

 character of an axis of volcanic eruption. 



In this manner it may be explained why areas of elevation 

 are older than the mountain ranges we find upon them, why 

 mountain ranges are thrown up along sea-coasts — an almost 

 certain evidence of the existence of lateral pressure exerted 



