HAS THE EXTENT OF LAND SURFACE BEEN INCREASI:NG] 205 



Section V. — Has the Exte^it of Land Surface on the Globe been on the ivhole 

 increasing with the Lapse of the Geological Ages? 



It having been shown in the preceding section that precipitation depends 

 — in part, at least — on the relative extent of land and water snrfiice on the 

 globe, the inquiry next suggests itself, whether we have reason to believe 

 that this relation has undergone a change with the lapse of the geological 

 ages ; and, if so, in what direction. Have the continents grown larger, or 

 have they diminished in size ? Or, on the other hand, has the gain made 

 by the rise or formation of new land in one region been more or less than 

 counterbalanced by sinking in another quarter ? If it can be shown to be, 

 if not absolutely certain, at least altogether probable that, on the whole, the 

 tendency of geological events has been toward an increase of land-surface 

 on the globe, as the epochs followed one after the other, then we have here 

 correspondingly strong reason for believing that the amount of precipitation 

 must have diminished in a similar ratio, unless it can be shown that some 

 other cause aflfecting rain-foil has been, at the same time, working in the 

 opposite direction. 



A broad field of inquiry is thus laid open before us, and one which not 

 only connects itself in the most direct way with the topics embraced in the 

 present volume, but which also has intimate and interesting relations to 

 several other geological and zoological questions. It Avill not be possible 

 to handle the subject, at the present time, in anything like an exhaustive 

 manner ; but some general results can be indicated which will be of impor- 

 tance in connection with the problem before us. 



It would seem that the first step in the inquiry is not a difficult one to 

 take. So far as the continental masses at present existing on the globe are 

 concerned, it is hardly possible to deny that they have, on the whole, with 

 the lapse of geological time, been growing. We can make out, by means 

 of sections and geological maps, what has been the character and mode of 

 formation of the different deposits which have succeeded each other, and in 

 doing tliis we find among the stratified rocks, as we recede in geological 

 time, an ever increasing predominance of those containing organic forms of 

 such a character as to indicate cleai'ly the presence of the ocean at the time 

 the strata in question were formed. An exception to this statement must be 

 admitted in the case of the apparently abnormal appearance of a large area 



