THE WASTE AND GAIN OF THE DRY LAND. 403 



THE WASTE AND GAIN OF THE DRY LAND. 



THE following letter, respecting a former article in the Month- 

 ly, has been addressed to the Editor : 



Editor Popular Science Monthly : 



Does M. A. de L'Apparent's interesting address * on The Fu- 

 ture of the Dry Land exhaust all the factors of the inquiry ? Is it 

 certain, for example, that some at least of the greatest mountain- 

 chains have not in the main risen in elevation faster than the 

 eroding agencies have depressed them ? Are not some of them, 

 and those now among the boldest, admitted to have been uplifted 

 in comparatively recent times, geologically speaking more recent- 

 ly, for example, than the advent of some of the rivers which inter- 

 sect them ? Erosion must have commenced from the very begin- 

 ning of the upheaval and have continued to the present time ; yet 

 they grew in stature in spite of it, for no one now supposes that 

 the upheaval was a sudden one. Indeed, the persistence of the 

 river's " right of way " proves both the constant action of " the 

 elements " and the extremely gradual character of the upheaval. 

 If our planet, as some think, continues to slowly contract from a 

 once nebulous condition, its advancing age might be expected to 

 be marked by wrinkles, just as we know it to be. 



Again, is there not good ground for the conjecture that our 

 globe, however slowly, is approaching a state of desiccation such 

 as is manifested partially in our neighbor Mars and still more 

 notably in the moon ? f Is there not some lingering continuance 

 of the once active absorption ? Is there not, for example, reason 

 to believe that the proportion of sea area has in the main steadily 

 diminished and that upheaval of the land masses has steadily in- 

 creased since Silurian times ? 



To the lay reader this masterful and interesting paper of the 

 French savant seems a courteous invitation to one of his compeers 

 to take up the thread of his discourse at the point at which he 

 elects to leave it. George Henry Knight. 



Temple Court, New York. 



Other letters on this subject have been received, all of which 

 indicate that the matter has attracted more interest than was an- 

 ticipated. Our correspondents may find on closer examination of 

 M. de L'Apparent's paper that he avowedly presents it as covering 

 only one side of the question, and that, while he does not discuss 



* Popular Science Monthly, June, 1891. 



f Do not northern Africa and western Asia contain vast regions that have passed 

 from exuberant fertility to hopeless aridity even during the historical period ? G. H. K. 



