Page:Popular Science Monthly Volume 5.djvu/774

754 of the Cretaceous and Tertiary epochs. These facts are, that a great variety of forms appear to spring suddenly into existence, during those epochs, without the existence, in preceding epochs, of other forms from which 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 implied variations of species are endless, is called in question. The position assumed is that such variations are limited.

In "Some Historical Results of the Science of Language," Prof. A. S. Wilkins draws a very entertaining picture of the condition, customs, and manners, of the prehistoric Aryan people, from glimpses afforded by the implications of the words they had in use; his object being to show what light has been thrown upon the distant 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 Medicine," "Provençal 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.

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 the highest point in the State is but a little 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 systems of rivers, an eastern and a western system, emptying, the former into the Mississippi, and the latter into the Missouri. As there are no mountains, the rivers constitute 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 Lakes, those whose beds consist of depressions in the drift, dating from the glacial epoch, and Alluvial Lakes, formed by the action of rivers. In the second chapter we have a discussion of the origin of the drift, in which the evidences of its glacial origin are set forth with a degree 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 question of practical coal-deposits, and is confident that coal may be sought for over the whole of Southwestern Iowa, with reasonable 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. Explorations 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 facilitating 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 mineralogy, lithology, and chemistry. But space