AEOLIAN SAND-RIPPLES 



81 



small ridges in quite loose sand, 

 measurements were made : — 



The following 



Number of 

 Observation. 



3 



4 

 5 

 6 



7 

 8 



9 



lO 



II 



12 



Diameter of 

 Sand-grains 

 in Inches. 



^5 



1 



1 



FT 

 1_ 



54: 



?v 



Number of Sand- 

 Grains in the 

 Height. 



5 (calculated) 

 5 (counted) 



8 „ 



8 (calculated) 



7 

 5 or 6 „ 



8 (counted) 

 12 (calculated) 

 1 6 (counted) 



20 



Ratio of the 



Length to the 



Height. 



20 



i8 

 17 

 17 



20 

 26 



i8J 



17 

 1 8 (average) 



14 



(In the case of number 12 there were smaller ripples upon 

 the weather slope.) 



The indication afforded by this table is that the 

 ratio of length to height remains constant during 

 the growth of the ripples, or, in other words, that 

 the shape of the wind-eddy which moulds them 

 is not affected by their growth. The average ratio 

 of length to height is 1855, which, as has already 

 been pointed out, is the same as that of the sand- 

 waves with a wave-length of 30 feet — that is to 

 say, with linear dimensions 120 times as great. 

 I have appealed to travellers in desert regions to 

 make similar measurements of a series of great 

 dunes, but have not yet received any results. 



