380 CHESTER K. WENTWORTH 



cobbles^ resulting from abrasion in transportation. Angular 

 masses of rock of the same size are commonly called blocks or 

 slabs. The word bowlder is related to the English word bellow; 

 compare Swedish hullra, to rattle or roar. Equivalent terms in 

 several other languages carry similar ideas of rumbling or rolling 

 in their derivation. 



Cobble. — Cobble or cobblestone is used generally, both by 

 geologists, and in common speech, for a rounded stone smaller 

 than a bowlder and larger than a pebble. The term is a diminutive 

 of the word cob, meaning a rounded hump or knob, and related to 

 the German Kopf, for head. 



Pebble. — This term is a very ancient one which is used commonly 

 for rounded, transported rock fragments smaller than cobbles. 

 In the past it was more commonly used than it is at present for 

 rounded stones up to the size of bowlders. The tendency now is 

 to use the term cobble in an intermediate sense, as stated above. 

 Pebble is from the Anglo-Saxon papol, which meant something 

 small and round, perhaps akin to the Latin papula, a pustule. 



Granule.' — The term granule is here proposed by the writer 

 as a term for rounded rock fragments larger than very coarse sand 

 grains but smaller than pebbles. Rounded pieces too small to be 

 called pebbles have still been too large to be called sand grains 

 in the practice of most geologists. Granule is from the Latin 

 granulum, diminutive of granum, grain, meaning a little grain, a 

 pellet. In spite of apparent infehcity of meaning (Kttle grain), 

 this term was chosen as best adapted for this grade of material. 

 The term grit grain was considered for use in this sense, but was 

 thought less satisfactory. Grit is used in another sense, as for 

 fine sandstone of angular grain. It seemed undesirable to include 

 these grains either with small pebbles or with coarse sand grains, 

 and it is hoped that the term granule may fill an apparent gap in 

 the series of terms heretofore used. 



Sand grain. — The several terms made up by the use of adjectives 

 qualifying sand grain are self-explanatory. 



1 For explanation of the basis on which the sizes limiting the several grades were 

 chosen, see the text which follows. 



2 This term was suggested to the writer by Dr. Herbert A. Baker, of England. 



