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Spencer — Deformation of Iroquois Beach and 



the "Iroquois Beach,"* in memory of the aborigines who 

 trailed over its gravel ridges. 



The general structure of the ancient shore-lines is somewhat 

 fully described in "Ancient Shores, Boulder Pavements, etc."f 

 but let us here repeat some of the characteristics. Typically, 

 then ancient beach consists of a ridge of gravel and sand rising 



sometimes to twenty-five 

 feet or more above the fron- 

 tal plain, which further de- 

 scends lake ward (as in fig. 

 1.) Back of the ridge, 

 which rarely exceeds a 

 width of 500 feet, and 

 usually less, with a very 

 narrow crest, there is often 

 a lagoon-like depression, 

 The beach may be broken into a number of ridges (b or c). The 

 summit marks the height of the wave action. This barrier ridge 



may become a terrace, or it may pass into the form of a spit 

 across some valley (A or b, fig, 2). Again the ridge may be 

 p wanting, but the shore will 



be represented as a cut ter- 

 race (fig. 3), in front of 

 which a bowlder pavement 

 may frequently be seen (P.) 

 This pavement is also often 

 found in front of gravel 

 beaches. In places where 

 the former waters were 

 gnawing away the drift 

 shores, or where rocky promontories rose out of deep water, tru& 

 beach structure is wanting, or only represented by benches. 



* The name was first printed in Science, Jan. 27th, 1888, p. 49. 

 f By the writer, in Bulletin of the Geological Society of America, vol. i, 1879 r 

 p. 71. 



