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THE POPULAR SCIENCE MONTHLY, 



tion of the Cretaceous and Tertiary epochs. 

 These facts are, that a great variety of 

 forms appear to spring suddenly into exist- 

 ence, during those epochs, without the ex- 

 istence, in preceding epochs, of other forms 

 from Avhich they could have descended ; 

 and the presence of more highly-organized 

 forms than we are led to look for on the 

 grounds of either doctrine. The issue is 

 made in a special, not a general sense. 

 The general fact of evolution is taken for 

 granted, while the special fact, that the im- 

 plied variations of species are endless, is 

 called in question. The position assumed 

 is that such variations are limited. 



In " Some Historical Results of the Sci- 

 ence of Language," Prof. A. S. Wilkins 

 draws a very entertaining picture of the 

 condition, customs, and manners, of the 

 prehistoric Aryan people, from ghmpses 

 afforded by the implications of the words 

 they had in use ; his object being to show 

 what light has been thrown upon the dis- 

 tant past by the study of philology. 



Among the remaining essays, " Original 

 Research as a Means of Education," " The 

 Distance of the Sun from the Earth," " The 

 Limits of our Knowledge of the Earth," 

 " The Use of Steam," " Science and Medi- 

 cine," "Provengal Poetry in Ancient and 

 Modern Times," "The Judicature Act of 

 1873, in its Relation to the History of the 

 Judicial System of England," and "The 

 Peace of Europe," will prove of interest to 

 the general reader. 



Report on the Geological Survey of the 

 State of Iowa to the Thirteenth Gen- 

 eral Assembly, January, 1870; con- 

 taining Results of Examinations and Ob- 

 servations made within the Years 1866 

 to 1869. By Charles A. White, M. D. 

 2 vols, imperial octavo, pages 391 and 

 435. Price $10.00. Des Moines, Iowa : 

 Mills & Co. 



The first four chapters of this work are 

 devoted to the physical geography of the 

 State, which is admirably presented. In 

 the first of these the author considers the 

 surface features of Iowa, and gives in a 

 chart five profiles across the State, showing 

 elevations above low water in the Mississippi 

 at Keokuk. From these it appears that j;he 

 highest point in the State is but a httle over 

 1,200 feet above the lowest, and that these 



two points are nearly 300 miles apart. The 

 drainage of the State consists of two sys- 

 tems of rivers, an eastern and a western 

 system, emptying, the former into the Mis- 

 sissippi, and the latter into the Missouri. 

 As there are no mountains, the rivers con- 

 stitute the most conspicuous feature in the 

 physical geography of the State, and all its 

 irregularities of surface are due almost solely 

 to erosion by streams. The inconsiderable 

 lakes of Iowa the author divides into two 

 classes, viz., Drift LaTces^ those whose beds 

 consist of depressions in the drift, dating 

 from the glacial epoch, and Alluvial Lake.% 

 formed by the action of rivers. In the sec- 

 ond chapter we have a discussion of the 

 origin of the drift, in which the evidences 

 of its glacial origin are set forth with a de- 

 gree of clearness which is truly admirable. 

 The two remaining chapters of this first 

 part are devoted to the consideration of 

 soils and climate. The author offers no 

 opinion as to the origin of the prairies, but 

 he holds " without the least hesitation that 

 the real cause of their present existence in 

 Iowa is the prevalence of the annual fires. 

 If these had been prevented fifty years ago, 

 Iowa would now be a timbered instead of 

 a prairie State." 



In Part II., General Geology, the author 

 considers, among other points, the ques- 

 tion of practical coal-deposits, and is con- 

 fident that coal may be sought for over 

 the whole of Southwestern Iowa, with rea- 

 sonable hope of finding plentiful supplies at 

 available depths. The present known coal- 

 area of the State is about 7,000 square miles. 

 The existence of large quantities, of good 

 peat has also been fully demonstrated. Ex- 

 plorations for mineral oil or the precious 

 metals in any part of the State are almost 

 certain to end in failure. 



In Part III. of the first volume, and 

 Part I. of the second, those portions of 

 the State which have been examined in this 

 survey are, as far as practicable, subdivided 

 into regions that have common geographical 

 characters, for the purpose of faciUtating 

 their description. A general account of 

 each region is followed by separate and 

 more detailed descriptions of every county 

 within it, so far as they have been examined. 

 Finally, Part II. has four chapters on miner- 

 alogy, lithology, and chemistry. But space 



