December 25, 1914] 



SCIENCE 



933 



The new building for the Medical College 

 of Soutli Carolina, Charleston, was formally 

 transferred to the board of trustees of the 

 institution, November 18. The address of the 

 occasion was made by Dr. William S. Currell, 

 president of the University of South Carolina. 



Dr. John Henry MacCracken, syndic and 

 professor of politics in New York University, 

 has been elected president of Lafayette College. 

 In the same week Dr. Henry Noble MacCracken, 

 professor of English at Smith College, was 

 elected president of Vassar College. They are 

 the sons of Dr. Henry Mitchell MacCracken, 

 chancellor-emeritus of New York University. 



Professor S. F. Agree, of the Johns Hop- 

 kins University, has accepted the position of 

 chief of the Section of Derived Products in the 

 Forest Products Laboratory in Madison and 

 professor of chemistry of forest products in 

 the University of Wisconsin. 



Mr. De Forest Hungerford, instructor in 

 soils in the College of Agriculture, University 

 of Minnesota, has been appointed assistant 

 professor of agronomy in the College of Agri- 

 culture, University of Arkansas. 



DISCUSSION AND COBBESPONDENCE 

 rate of continental denudation 



At first glance nothing appears more simple 

 than the measurement of the discharge of a 

 large river, and from the volume of matter 

 found to be held in suspension and in solution 

 to calculate the annual depletion of the drain- 

 age basin. Ever since the first estimates of 

 Humphreys and Abbot, over half a century 

 ago, the Mississippi Eiver has been a favor- 

 ite illustration of this kind. Recent results of 

 more elaborate measurements of this character 

 made by the federal government are apparently 

 undertaken with the express purpose of deter- 

 mining the rate of lowering of the continental 

 surface through stream-corrasion. 



So soon as a concrete case is settled upon 

 there enters into the problem a number of new 

 and variant factors which, if not perfectly 

 evaluated, utterly invalidate the results sought. 

 In this respect the Mississippi Valley appears 



to be the most unfortunate choice' that it is 

 possible to select. Although the recently pub- 

 lished results seem to give excessively small 

 figures and the established rate very much too 

 slow, it is to certain other features that atten- 

 tion is here briefiy called, which appear not 

 to have entered into the calculations named. 



According to the figures referred to it would 

 take some millions of years to reduce the 

 already low-lying Mississippi basin to the con- 

 dition of a true peneplain with a position but 

 slightly above tide-level. All direct geologic 

 observations made during late years in the 

 region go to show rather conclusively that in 

 reality the surface of the vast basin is on the 

 whole actually rising instead of becoming 

 notably lower. 



Among other factors it appears that the 

 wind-borne dusts from western deserts are 

 alone probably depositing materials over the 

 entire Mississippi Valley faster than the river 

 and its tributaries are carrying rock-waste to 

 the sea. In recent geologic times, also, the 

 western half of the basin has actually had 

 deposits laid down upon its surface to a thick- 

 ness of not less than 1,000 feet. The great 

 river has not only not been equal to the task of 

 doing its normal amount of work, but it has 

 been so incapacitated as to permit this prodi- 

 gious volume of rock-waste to accumulate 

 until its original Tertiary surface is already 

 carried far below sea-level. Nowhere on earth 

 is there finer exemplification of vast conti- 

 nental sedimentation. 



In the lately compiled estimates of conti- 

 nental lowering several diastrophic factors 

 are left out. These are extremely important 

 in all calculations of this kind. Since Glacial 

 times — perhaps 10,000 years ago — a very con- 

 siderable part of the upper Mississippi Valley 

 appears to have been elevated not less than 

 500 to 600 feet. This change of level may 

 represent the isostatic compensation of the 

 last great ice-cap. At any rate, while there has 

 been over this region an erosive loss of a frac- 

 tion of a foot each century, there has been in 

 the same time a gain in sediments of many 

 times this amount. Growth has exceeded de- 

 cline a hundred-fold. 



