86 Scientifio Intelligence. 



It is to be hoped tliat tlie reconnaissance survey is to be fol- 

 lowed by detailed work, which will result in a fuller knowledge 

 of this interesting and nnknovvn region. n. e. g. 



4. Corrosion hy Graviti/ Streams with Applications of the 

 Ice Flood IlyjMthesis ; by E.G. Andrews, Department of Mines, 

 Sydney. Reprinted from Journal and Proc. of the Royal Society 

 of N. S. Wales, vol. xliii, pp. '204-330, with 11 figs., 3 appendices 

 and a bibliography. — Tl)is is an important paper which should 

 be called to the attention of American geologists interested 

 in surface processes. The author is best known by his pre- 

 vious paper on the Ice Flood Hypothesis,* in which he main- 

 tained the excessive erosive power of glaciers during their period 

 of maximum development, or flood, as compared with their weak 

 erosive effects during stages of recession. In the present paper 

 he takes up the subject of stream erosion more broadly as the 

 action of the gravity stream, irrespective of the fluid or solid 

 Avhich composes it, and discusses the laws of its movement. To 

 sum w^ the results of his conclusions it may be noted, — that 

 U-shaped valleys and cirques are forms characteristic of maxi- 

 mum or flood erosion and are not forms solely dependent upon 

 ice as a medium. P^ven where the stream of ice or water covers 

 a region broadly it will erode unequally. During the flood stages 

 it shows an excessive effect upon the bottoms of the principal 

 channels in contrast to its flood plain and increases the relief of 

 the region. During drought stages aggradation tends to take 

 place within these overdeepened and oversteepened channel walls. 

 Through the formulation of these principles the author discusses 

 changes in the character of glacial erosion between the ice age 

 and the present, and draws distinctions between those features 

 which are essentially peculiar to ice as a medium. Applications 

 of his discussions resulting in some new conclusions are made, 

 among other regions, to the California Sierras, the Finger Lake 

 region, the St. Lawrence and the Hudson Rivers. 



As the original paper may be difl[icult of access to many who 

 may wish to quote some of Andrews' statements, the following 

 conclusions are quoted, the bearing of which may be better appre- 

 ciated in the light of the preceding statements: 



"A. Inducti))e Studies. — (1) Cirques, hanging valleys, rock 

 basins, facetted spurs (or spurless walls), smoothed cols, "steps," 

 and " treads" occur in all recently glaciated regions. (2) In pro- 

 portion to the intensity of the recent glaciation so are these pecu- 

 liar land profiles pronounced in number, size, and appearance. 

 (3) In localities not glaciated recently such peculiar land profiles 

 are absent. (4) All these forms are matched in miniature along 

 any channel determined by thunderstorm waters. (5) Along the 

 beds of even large stream channels similar forms occur to those 

 lust enumerated. (6) The forms in all these cases are similarly 

 situated with respect to their enveloping channels. (7) The 

 forms in each case are adjusted to the size of the various stream 



* Jour. Geol., vol. xiv, pp. 22-54, 1906. 



