EOLIAN HYPOTHESIS CONCERNING LOESS. 9 
casional overlapping of the loess on the Iowan till. The gradual transitions from 
underlying terranes which often merge, as it were, into the base of the loess, would 
naturally be formed as the conditions for the accumulation of the loess slowly set 
in. Thus we should expect to find under the loess here and there the oxidized sur- 
face of the older till, old soils, forest beds, peat, overwash aprons, dune sand, etcetera. 
The loess itself ought to be heaviest and coarsest along the larger drainage chan- 
nels, where the topography has aided in producing local wind eddies and where 
the rivers have helped to expose materials to wind action. The water of these 
rivers may have added a part of the material in some places along their courses. 
This is indicated by occasional stratified phases of the loessin such localities. The 
multiple age of the loess is also easily accounted for, as with the many climatic 
changes attendant upon the periods of the ice age, conditions may readily at dif- 
ferent times so far have favored the work of the wind as to have allowed the ac- 
cumulation and the preservation of its sediments. 
The paper was discussed by J. W. Spencer, G. F. Wright, EK. W. Clay- 
pole, G. K. Gilbert, and Frank Leverett. 
Following the discussion of Mr Udden’s paper, at 12.15 o’clock the 
Society adjourned for the noon recess. 
At 2.15 o’clock p m the Society was again called to order, and in the 
absence of President Orton Mr G. K. Gilbert was elected temporary chair- 
man. 
The following paper was read: 
ANALOGY BETWEEN DECLIVITIES OF LAND AND SUBMARINE VALLEYS 
BY J. W. SPENCER 
At the conclusion of the reading President Orton resumed the chair. 
The next paper was by the same author: 
GREAT CHANGES OF LEVEL IN MEXICO AND THE INTEROCEANIC CONNECTIONS 
BY J. W. SPENCER 
The paper is printed in full in this volume. 
The two papers by Mr Spencer were discussed together, and remarks 
were made by EH. W. Claypole, W. N. Rice, and G. K. Gilbert. 
The following paper was read : 
ORIGIN OF ThE GORGE OF THE WHIRLPOOL RAPIDS AT NIAGARA 
BY F. B. TAYLOR 
The paper is printed in full in this volume, 
JI—Butt. Gror, Soc. Am., Vou. 9, 1897 
