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PROCEEDINGS OF THE ALBANY MEETING 



considered between rock ledges and river terraces had not before been an- 

 nounced. It has since then been found that the essence of the relation has been 

 stated in a paper by Hugh Miller.* The present note must therefore serve chiefly 

 to make Miller's paper better known to American readers by showing the applica- 

 tion of his theory to American examples, as well as to suggest that the plains of 

 our New England terraces do not indicate gradation with respect to temporary 

 baselevels and that the arrangement of terraces in flights of steps does not depend 

 on the diminution of stream volume, however true it may be that stream volume 

 has diminished during the process of terracing. 



FiGTRE 1. — Block Diagrnm nf River Terraces 



A flight of terrace steps defended by sucee.ssive outcrops of a long, sloping ledge in the back- 

 ground. A single high terrace formed by the consumption of all the earlier made terraces in 

 the foreground. Two ledge-ilefended low-level terrace cusps below a higli terrace in the 

 center. 



In a valley whose cross-section shows several terraces at successive heights, it is 

 necessarily the case that the breadth of the interscarp space between the high- 

 level terraces is greater than that between the low-level terraces. Besides Miller's 

 theory, two others are current for the explanation of this feature. One theory 

 postulates a once greater volume for the terracing riVer. At first, when large, the 

 river is supposed to swing broadly from side to side and thus open a wide inter- 

 scarp space; later, when the valley had been eroded to a greater depth and the 

 volume of the stream had decreased, the river is contented with a smaller width 



* River-terracing : Its methods and their results, Proc. Roy. Phys, Soe. Edinburgh, 1883, vol. vii, 

 pp. 263-306. 



