PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



GEOLOGICAL SOCIETY OF WASHINGTON 



33 8th meeting 



The 338th meeting of the Society was held in the auditorium of the 

 Cosmos Club on Wednesday evening, May 28, 1919, at 8 p.m. 



Informal Communications 



Mr. LaForge spoke of a fairly wide-spread misapprehension of the 

 exact meaning of the words talus and shingle and the resultant in- 

 creasing tendency to use them incorrectly. Talus seems to be used to 

 some extent in the United States for the material which in reality 

 constitutes a talus. The word is synonymous with scree which is 

 commonly used in Great Britain. It means "a heap of coarse rock 

 waste at the foot of a cliff or a sheet of such waste on a slope below a 

 cliff," and its use should be confined to the heap or sheet and not 

 extended to the constituent material, which is rock waste. 



There seems to be a rather general idea that shingle means gravel com- 

 posed chiefly of flattened pebbles which have been arranged by gravity, 

 waves, or currents so as to overlap like shingles on a roof. This is 

 entirely incorrect, as the word has no relation to the ordinary English 

 word shingle (originally shindle), but is derived from the same Germanic 

 or Norse root from which comes our common word sing, the h having 

 been introduced through corruption, and it refers to the peculiar sound 

 made by the material when trod upon or when rolled down the slope 

 of the beach by a receding wave. 



This brings up the question regarding the origin of the sound, and, 

 therefore, regarding the essential or distinctive character of shingle. 

 The dictionaries and those text-books which define the word state that 

 it is "beach material coarser than ordinary gravel," but manifestly 

 such a definition is inadequate, as some "singing" beaches consist of 

 fine material and many beaches composed of coarse gravel do not 

 "sing." Apparently the subject has not been investigated experimen- 

 tally, but the number of field observations have led the speaker to the 

 following tentative hypothesis : 



The production of a sound approximating a musical note requires 

 a certain degree of uniformity in the sound-making material and the 

 pitch of the sound depends on the dimensions of the material, and of 

 the resonating space, if there be any. To have such uniformity it is 

 therefore necessary that the pebbles be of approximately the same 

 size, hence the interstices will not be filled with finer material, as in 



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