396 PROCEEDINGS OF THE CALIFORNIA MEETING 



history, economic life, and probable future movements of various Philippine 

 tribes. Some comparisons were drawn between Malaysian geology and that 

 of the west coast of America. 



Eead in full from manuscript. 



Discussion 



Prof. R. A. Daly offered expressions of appreciation and inquiries as to 

 relations of recent to Tertiary coral reefs. 



Professor Smith replied that no break or- disconformity has been noted in 

 the coral formation of the Philippines. 



Prof. A. C. Lawson asked if there are special types of topography in these 

 regions of excessive rainfall. 



Professor Smith called attention to the fact that in Luzon valleys are Y- 

 shaped and contain no soil. 



Further remarks were made by Professors William H. Hobbs and C. F. 

 Tolman, Jr. 



ORIGIN OF THE BASINS WITHIN THE HAMADA OF THE LIBYAN DESERT 



BY WILLIAM HERBERT HOBBS 



{AT)Stract) 



The intense aridity, the nearly uniform wind direction throughout the year, 

 and the small areas of many of the basins when compared to that of the sur- 

 rounding hamada are conditions which greatly facilitate a solution of the 

 problem of origin. In the distribution of the trains of sand-dunes and of the 

 deposit of loess, reason is found for believing that the basins have resulted 

 from deflation which has been initiated wherever local faulting has so dis- 

 turbed the hard mesa capping of Mokattam (Eocene) limestone as to bring the 

 inferior and soft Cretaceous shales under the influence of the undermining 

 action of the sand-blast. 



Presented in full extemporaneously. Discussion was deferred. 



LIMITED EFFECTIVE VERTICAL RANGE OF THE DESERT SAND-BLAST, BASED 



ON OBSERVATIONS MADE IN THE LIBYAN DESERT AND IN 



THE ANGLO-EGYPTIAN SUDAN 



BY WILLIAM HERBERT IIOBBS 



(Abstract) 



Observations made at numerous localities in northeastern Africa indicate 

 that the effective action of the desert sand-blast does not there extend to 

 a height of more than a meter above the surface of the ground. Some expla- 

 nation for the sharp delimitation of this action was offered. 



Presented in full extemporaneously. Discussion was deferred. 



