276 N. S. SHALER — SPACING OP RIVERS 



have been able to examine the effect ari.sin<j; from the interaction of the 

 slopes of rivers spaced with an approximation of equality in interval 

 and with like declivities will more satisfactorily account for the uni- 

 formity of elevation than tlie hy[)othesis which seeks to explain the 

 coincidence by ancient baseleveling, with sul)sequent I'eelevation and 

 denudation. It may well be that in many instances the results of the 

 two fvroups of actions are intermingled. 



