TITLES AND ABSTRACTS OF PAPERS 73 



Aside from the presence of an ice-table, snowfall is probably one of the 

 essential conditions prerequisite to solifluction in high latitudes. Snowfall and 

 gradual, but not rapid, melting of the snow make solifluction possible. 



Distinction should be made between solifluction which causes progressive 

 motion of surface materials, such as results in altiplanation terraces, solifluc- 

 tion slopes, and soil-streams or soil-glaciers, and that which causes only circu- 

 latory movement, such as results in "polygonboden." It is the first of these 

 forms of solifluction which is one of the most important transporting agencies 

 in northern Greenland. On every land area of the ice-free coast the landscape 

 presents evidences of the wide-spread activitj'^ of this agency. 



Eead in full from manuscript. 



PRESENT STATUS OF THE PROBLEM OF THE ORIGIN OF LOESS 

 BY C. W. TOMLINSON ^ 



(Adstract) 



A critical analysis of existing opinions on the origin of loess, with a sum- 

 mary of the evidence thus far presented, the conclusions derived therefrom, 

 and suggestions for further study. 



Presented in full extemporaneously. 



Discussion 



Mr. Frank Leverett spoke of the advisability of restricting the term loess 

 to wind deposits of uniform texture and not to include wind deposits in which 

 sand and silt are mingled. 



Dr. J. L. Rich : Inasmuch as ants and several kinds of burrowing animals 

 are constantly bringing sand and small pebbles to the surface from depths of 

 two or three feet, it seems to me that any thin deposit of loess, three feet or 

 less thick, would almost certainly be a mixture and would contain consider- 

 able coarser material, even if deposited as fine, wind-borne dust, and therefore 

 that a distinction on a genetic basis between this and true loess, such as is 

 suggested by Mr. Leverett, can not be made. 



Dr. A. R. Crook : I should like to inquire if there are many data concerning 

 the per cent of solubility of loess in hydrochloride and in various parts of the 

 world, since this would shed light on the source or distance of transportation 

 of the material constituting the loess. 



Mr. J. H. Lees : Professor Shimek shows in Iowa Academy of Science, volume 

 24, that there probably is no loess in Bohemia. The material which has been 

 called loess by the Bohemian geologists is waterlaid and the geologists them- 

 selves are now of the opinion that it is not true loess. 



Mr. W. H. Bucher : On the sides of the Rhine Valley graben the mixed 

 character of the loess is in numerous exposures seen to be intimately con- 

 nected with the proximity to hill and mountain slopes from which rain occa- 

 sionally washed pebbles and talus material on top of growing loess deposits. 

 Such material, although transported by water, only emphasizes the subaerial 



Introduced by Eliot Black welder. 



