Maech 12, 1897.] 



SCIENCE. 



437 



CURRENT NOTES ON PHYSIOGRAPHY. 

 CAMPBELL ON DRAINAGE MODIFICATIONS. 



The processes whereby rivers re-arrange 

 their courses when the region that they 

 drain is aiiected by gentle deformation is 

 thoroughly treated by M. E. Campbell 

 (Chicago Journ. Geol., IV., 1896, 567-581, 

 657-678). He gives a detailed deductive 

 consideration of expected changes, leading 

 to the 'law of the migration of divides ;' 

 in brief, that divides migrate towards an 

 axis of uplift. It is further shown that, 

 under the influence of tilting, rivers will, 

 by the migration of divides, tend to arrange 

 themselves in rectangular pattern, the 

 smaller streams running down the dip, the 

 larger along the strike of the tilt. Streams 

 are most sensitive to these influences in 

 their old age, when, by long striving, each 

 individual has come to be so delicately bal- 

 anced against its neighbors that the least 

 outside influence may cause predatory con- 

 quests by the more favored. Several exam- 

 ples are given of rivers in the Appalachian 

 region which appear to have been affected 

 by changes of the kind here discussed ; 

 among these the Chattahoochee, ISTew and 

 Eoanoke rivers being especially interesting. 



To the student of the natural history of 

 rivers this discussion by Campbell must be 

 particularly acceptable, inasmuch as it in- 

 troduces the competent consideration of an 

 element of disturbance not sufBcientlj^ at- 

 tended to in earlier studies of the develop- 

 ment of river courses. 



Russell's glaciers of north America. 



Under the above title Professor I. C. Rus- 

 sell has prepared another 'reading lessons for 

 students of geography and geology' (Ginn & 

 Co., Boston, 1897), a companion to his 

 Lakes of North America, and has thereby 

 placed teachers and students alike under 

 many obligations to him. Good geograph- 

 ical literature, neither in text-books nor in 

 advanced professional reports, but in acces- 



sible and attractive form for ready use, is 

 so rare that teachers are often at a loss 

 where to find it ; and students who reach 

 an impressible, interrogative attitude are 

 perforce left unsupplied with answers to 

 their questions. It is only as books like 

 these ' lessons ' of Eussell's increase in 

 number that the studious treatment of 

 geography can flourish. This book on 

 glaciers is doubly welcome at the present 

 time of a growing interest in geographical 

 science. We find first a general account of 

 glaciers and of their modern and ancient 

 action ; then several chapters on the exist- 

 ing glaciers of various districts in N^orth 

 America, the brevity of the chapter on 

 Canada pointing clearly to that district as 

 most in need of further exploration. Clos- 

 ing chapters discuss climatic changes indi- 

 cated by glaciers, why glaciers move, and 

 the life history of a glacier; the latter being 

 especially recommendable from its novelty 

 and breadth of view. The book contains 

 many excellent illustrations. 



the gohna landslip. 

 A REMARKABLE instance of foresight in 

 averting disaster is found in an account of 

 the Gohna landslip on a head branch of 

 the Ganges, in the Garhwal Himalaya, and 

 of the flood that followed on the overflow 

 of the resulting lake, as published by the 

 Public Works Department of the Govern- 

 ment of India (Calcutta, 1896). The slip 

 occurred in September, 1893, continuing 

 three days with deafening noise, darkening 

 the air with the dust from shattered rocks, 

 and clogging the narrow valley with 800,- 

 000,000 tons of detritus. The fall de- 

 scended about 4,000 feet, spreading about 

 two miles along the valley and rising 850 

 feet above the former stream level. It re- 

 sulted from the undercutting of strata that 

 dipped into the valley, and hence should 

 be classed with those slides that follow the 

 erosion of narrow valleys in uplifted 



