Reviews — Foster^ s Mississippi Valley. 421 



It is satisfactory to know that there exists within easy reach of 

 London a supply of the best and purest spring water which, in case 

 of need, could readily be rendered available as an auxiliary source 

 of water-supply for the Metropolis, in quantity sufficient at all events 

 for drinking, if not for other purposes. 



I^EATIE^V^S. 



I. — The Mississippi Valley : its Physical G-eography, including 

 Sketches of the Topography, Botany, Climate, Geology, and 

 Mineral Eesources ; and of the progress of development in 

 population and material wealth. By J. W. Foster, LL.D. 

 Illustrated by maps and sections. Chicago : S. C. Griggs & Co. 

 London : Triibner & Co. 1869. 8vo. pp. 444. 



THE author, having devoted many years to the exploration of the 

 Mississippi valley, describes in the volume before us the phy- 

 sical geography of that portion of this wonderful region which lies 

 west of the great dividing line — the Mississippi River. 



It was with a view of illustrating the gradations between the 

 forest, prairie, and desert; the varying conditions of temperature 

 and moisture, and their effects in determining the range of those 

 plants cultivated for food ; and, at the same time, to trace the cha- 

 racter of the fundamental rocks over the whole of this region, point- 

 ing out the mode of occurrence of those ores and minerals useful in 

 the arts, and, finally, to trace the colonization of this region from 

 its feeble beginnings to its present magnificent proportions, that 

 this work was undertaken by Dr. Foster. 



It is not intended to be a strictly scientific work, but rather to 

 present a series of sketches of the great phenomena of the region 

 under consideration in a form which should at once interest and 

 instruct the general reader. 



Among the many chapters calculated to interest the general 

 reader there are some which may be considered as more especially 

 attractive to the physicist and geologist. Of these we might men- 

 tion, firstly, the chapters in which the author discusses the origin of 

 prairies, including not only those of the great Mississippi basin but 

 also those of South America and other countries. 



Dr. Foster discusses the various views put forth by other authors 

 as to their origin, whether as due to peat-growth, texture of soil, or 

 annual burnings ; and concludes, after a careful consideration of all 

 the conditions, that " a study of the physical features of the coimtry 

 in connection with the prevailing winds, the consequent distribution 

 of moisture, and also the lines of equal temperature, will show — 

 firstly, that these great changes in the geographical distribution of 

 plants, under nearly equal lines of temperature, are not due to the 

 mechanical texture or chemical composition of the soil, but to the 

 variable supplies of moisture ; secondly, that in the winds, as the 

 agents in the distribution of that moisture, we have an adequate cause 

 to explain all the phenomena of forest, prairie, and desert." 



