August 18, 1916] 



SCIENCE 



239 



tions of glacial climate, and, on the other 

 hand, conditions of arid climate. 



Limitations to the normal geographic cycle 

 are even more severe than these bare state- 

 ments intimate. If the United States, for in- 

 stance, be divided into three north and south 

 belts of subequal size one of the divisional 

 lines coincides with the course of the Missis- 

 sippi River; and the other with the line of the 

 Rocky Mountain front. The belts are each 

 approximately one thousand miles in width. 



In the easternmost of these belts the forces 

 of normal landscape sculpturing are most 

 active. The rivers at the present time are 

 wearing down the mountains and hills towards 

 base-level about as rapidly as is done any- 

 where else on the face of the globe, and about 

 as fast as it is ever done. 



In the ce'ntral belt, the tract lying between 

 the Great River and the Rocky cordillera, the 

 streams traversing the region are far from 

 doing normal corrasive work or of producing 

 net results. Between the Canadian and Mexi- 

 can boundaries, a distance of more than 2,000 

 miles, only five streams leave the Rocky Moun- 

 tain front, and four of these are quite incon- 

 siderable. They can have relatively little influ- 

 ence in the effort to base-level so vast a region 

 as the Great Plains. Dust and sands from 

 western deserts are constantly exported to this 

 region. In fact, lying on the leeward side of 

 the arid lands the Great Plains country is a 

 chief area of wind-laid depositions. The con- 

 tinental deposits over much of the region are 

 more than 1,000 feet thick, a fact amply attest- 

 ing the prodigious extent and the unusual 

 rapidity of their formation. This circum- 

 stance alone explains the excessively slow rate 

 of continental denudation which the recent 

 government stream-measurements of the Mis- 

 sissippi River give. The normal geographic 

 cycle does not obtain in this region. 



In the westernmost belt the general lower- 

 ing and leveling effects of rivers are inappre- 

 ciable. Water-work is reduced to its lowest 

 terms. Wind is the mastering erosive agency. 

 The geographic cycle has for its dominant ele- 

 ment wind-scour instead of stream-corrasion. 



The idea has a still broader bearing. It has 



world-wide application. According to the late 

 Sir John Murray more than one fifth of the 

 entire land surface of the globe is desert. An- 

 other one fifth and more is little affected by 

 normal river corrasion. Still another one fifth 

 of the land surface is, or at least was until very 

 recent geologic times, as truly desert as is the 

 Sahara to-day. Of all the world's land area, 

 therefore, fully two thirds are not subject to 

 normal stream-work; and the normal geo- 

 graphic cycle is without verity. 



Charles Keyes 



ugo schiff 



In Science, June 30, 1916, page 922, Pro- 

 fessor Wm. McPherson, in his obituary notice 

 of Ugo Schiff, says : 



This recalls the fact also that Professor Baey- 

 er 's laboratory at Munich did not include any lab- 

 oratory devoted to physical chemistry until 1913, 

 when a small room was fitted up for this work. 



Professor McPherson is mistaken. During 

 a number of years before and after 1887, 

 Kriiss gave, in Baeyer's laboratory, courses of 

 lectures and laboratory work in physical chem- 

 istry. The complete courses ran through sev- 

 eral semesters and the experimental exercises 

 were given in a room specially fitted. They 

 included density determinations of solids, 

 liquids and gases, by various methods, cryo- 

 scopic molecular weights, spectroscopic work 

 (emission and absorption), optical rotation, 

 etc. Probably no better courses were given 

 anywhere, at that time, outside Ostwald's 

 laboratory. It may well be that Kriiss's pre- 

 mature death caused the courses to be dis- 

 continued. J. Bishop Tingle 



McMaster University, 

 Toronto, Canada. 



SCIENTIFIC BOOKS 



The Origin of the Earth. By Thomas 

 Chrowder Chamberlin, head of the Depart- 

 ment of Geology, The University of Chicago. 

 The University of Chicago Press, 1916. 

 Pp. x-f 271. (The University of Chicago 

 Science Series.) 

 This book, by the distinguished author of 



the planetesimal hypothesis, is one which has 



