REVIEWS 583 



obliterated by the advance of the ice to the Manistee moraine. These higher 

 beaches seem to have suffered httle or no tilting. 



The Lake Algonquin beaches seem to extend southv/ard through Wisconsin 

 v/ith rapidly diminishing inclination south of Sturgeon Bay, becoming horizontal 

 near Tv/o Rivers, and encircling the southern half of Lake Michigan as the 

 "Toleston" beach. This makes the Chicago outlet an outlet for Lake Algon- 

 quin at its highest stage. 



The Nipissing v/ater-plane seems to stand nearly horizontal along the v/hole 

 Wisconsin shore — absolutely horizontal, and 10 or 15 feet above the lake, south of 

 Manitov^oc. 



The elevation of the various beaches was determined by means of the 

 wye level, thus reducing the chances for misinterpretation to a minimum. 



H. H. 



Some Characteristics of the Glacial Period in Non-Glaciated Regions. 

 By Ellsworth Huntington. Bull. Geol. Soc. of Am., Vol. 

 XVIII, pp. 351-88, pis. XXXI-XXXIX. New York, 1907. 



This significant article is rendered particularly valuable because of the 

 author's exceptional opportunities for the observation of arid conditions 

 in two continents. It is evident, the whole earth considered, that fluctua- 

 tions of the ice-edge were far from being the only effects of the climatic 

 changes of the Pleistocene. In some of the now desert basins of central 

 Asia are evidences of a surprising number of oscillations of lacustrine and 

 arid conditions, some apparently coinciding with the known alternations 

 of glacial and interglacial stages of the so-called Glacial period, and others 

 preceding them. H. H. 



The Clays of Mississippi. By William N. Logan. Mississippi 



Geological Survey, Bulletin No. 2. 250 pp., 42 pis., 14 figs, 



Jackson, 1907. 



This bulletin contains chapters on the origin, classification, chemical 



and physical properties, and processes of manufacture of clays, on the 



properties and imperfections of brick, on the geology of Mississippi clays, 



and on the clay industries of the northern part of that state. H. H. 



A Theory of Continental Structure Applied to North America. By 

 Bailey Willis. Bull. Geol. Soc. of Am., Vol. XVIII, pp. 389- 

 412. New York, 1907. 



An analysis of the North American continent is taken to show that it 

 may be resolved into a number of positive, or Hghter, and of negative, or 



