204 E. C. ANDREWS. 



OORRASION by GRAVITY STREAMS with APPLI- 

 CATIONS of the ICE FLOOD HYPOTHESIS. 



By E. 0. Andrews, b.a., Department of Mines, Sydney. 

 Parts I, II, III. 



[Read before the Royal Society of N. S. Wales, November 3, 1909.'] 



Table op Contents — Part I. 

 Introduction — The difficulties attendant on scientific studies. 

 The value of analogy in scientific pursuits. Comparative stream 

 studies. Certain principles are common to gravity streams. 



Summary of Stream Characteristics. — The Gravity Stream. 

 Surface of Stream. Channel base. Increase of stream volume. 

 Path of a stream particle. Valley constrictions, " confluences," 

 "broads" and "diffluences." Transportation of Material. Stream 

 motion round obstacles. Differential motion and shearing. 



Corrasion by Streams — Preliminary. — The terms corrasion and 

 aggradation distinguished. Principles common to stream cor- 

 rasion : — 



(i) Stream transportation and energy as related to increase 



of velocity, 

 (ii) Strengths of streams and rock structures compared. 



Geological Assumptions. — Homogeneous rock textures, struc- 

 tures, and mineralogical composition. 



A. Initial corrasive forms (for streams possessing constant 

 volume). 

 (a) Along channel bases of negligible slope and at locations of 

 channel constrictions . 



(i) Along valleys arranged symmetrically to a 



central vertical plane, 

 (ii) At a constriction determined by stream con- 

 fluence. The lateral, vertical and longitudinal 

 measures of stream strength — basins formed, 

 details of basin profiles, cirque or cup-shaped 

 heads. 



