REVIEWS 609 



continued sunken or sinking condition, and it appears not to be separated from the 

 recent alluvium by any sharp line of demarkation. The lower limits also are not 

 clearly shown, there being a transition into the Lafayette. Loess is thought to be repre- 

 sented at a few localities. The loess and the Port Hudson have been raised to 

 moderate altitudes above the sea, and the deposits made in trenches cut in these for- 

 mations constitute practically the last geological formation. 



The mud lumps at the mouth of the Mississippi are briefly discussed and shown 

 to be unlike volcanic cones running down outside a gas vent. They represent 

 upheavals, produced probably in large part by gas, though the origin and agencies are 

 not fully understood. 



The water supplies from the Quaternary are discussed on pp. 215-52. The 

 Lafayette sands afford a strong supply, and if overlain by the Port Hudson clay, the 

 water usually shows a rise when struck. The head declines toward the Gulf and also 

 toward the axis of the embayment. 



Upham, Warren. Growth of the Mississippi Delta. Am. GeoL, Vol. XXX, 

 pp. 103-1 I, 1902. 



The data collected from notes of early explorers lead to the conclusion that in the 

 four centuries since the delta was seen by Vespucci it has been extended in the passes 

 some 10 or 15 miles. The extension of the delta from an old to a new group of 

 branches or passes is thought to have been effected by the growth of one of the old 

 passes so far beyond the others that it became the chief, if not the only, channel in 

 ordinary stages of the river. It is predicted that, instead of extending forward in a 

 third stage, the main current will forsake this lower course and descend to sea level 

 some shorter way. 



GENERAL. 



Dryer, Charles R. Lessons in Physical Geography. 430 pp., 347 text 



Figs., and 20 full-page maps. New York : American Book Co., igoi. 



The subjects treated are the earth as a planet, the land, the sea, the atmosphere, 

 and life. 



The aim of the book is to develop a scientific habit of mind in the study of phvs- 

 ical geography. No attempt is made to discuss exhaustively the physical features of 

 the earth, or of any special region ; but the best type-forms are selected and treated 

 with sufficient fulness to give a clear and definite picture. General laws are developed 

 from a study of the type which may be applied wherever the problems to which they 

 apply may arise. This plan makes it possible to avoid the vague generalizations which 

 characterize too many text-books. A large number of realistic exercises are intro- 

 duced which appeal to the actual or possible experience of a student. They aim to 

 give some idea of the methods of geographic research, and include both field and 

 laboratory work. The illustrations, which are many, are frequently drawn from the 

 interior part of the United States, which has been poorly represented in previous 

 works on physical geography. 

 EcKHOLM, N. Meteorological Conditions of the Pleistocene Epoch. London 



Quart. Journ. Geol. Soc, Vol. LVIII, pp. 37-45. 1902. 



The area of Pleistocene glaciation in Europe and America corresponds with the 

 areas now traversed regularly by frequent storm tracks. There seems to have been 

 the same difference in mean annual temperature of Europe and America in the Ice 

 age as now, and it is thought a lowering of the temperature sufficient to put the snow 



