14 



GLACIAL GliAVELS OF MAINE. 



them. It has been estunatecP that the transporting power of different rates 

 of river flow is as follows : 



Transjiorting xmwer of different rates of river flow. 



The specific graAdty of the gravelstones is not stated, but presumably 

 it is that of ordinary rocks. 



The fragments transported by Avater are of A'arious sizes, and have 

 received names accordingly. The folloAving names have been proposed by 

 Prof. T. C. Chamberlin: 



For the A^ery finest particles, mud or clai/; for fragments up to size of a 

 pea, sand; for fragments A^arying from the size of a pea up to about 1 inch 

 in dinmeter, fine gravel; for fragments from 1 inch to 3 inches in diameter, 

 coarse gravel; for rounded stones less than 3 inches in diameter, peVbles; for 

 rounded stones from 3 to 6 inches in diameter, cobbles; for masses from 

 6 inches to 15 inches in diameter, hoivlderets ; for masses over 15 inches in 

 diameter, boivlders. 



In this report stones from the size of a pea up to 1 inch in diameter 

 are called gravelstones, and the transitions between mud and sand are 

 termed silt. 



That rivers are carrying drift matter to the sea is a matter of common 

 observation. Tlie sound of gravelstones and pebbles rattling against one 

 another and rolling along' the bottom of the upper courses of streams can 

 often be heard by one who puts his ear near the bottom of a boat or into 

 the water. Everyone has seen streams tear down portions of their banks 

 and carry them away. The muddy color of many streams, especially in 



'David Stevenson, Canal .ind River Engineering; quoted by Geikie, Text-book of Geology, 

 p. 380, 1893. 



