54 GEOLOGICAL SURVEY OF WISCONSIN. 



referred to as indicating changes that have taken place in the condi- 

 tion of the land in remote times. 



The drainage is shown to be a proper medium between the slow- 

 fiowing streams and swamps of a flat country, requiring artificial 

 drainage, and the rapid currents of highly inclined lands, causing ex- 

 tensive erosions and the loss of the more fertile portions of the soil. 



Attention is given to the fact that large areas represented as marsh 

 on the government plats are now dry and arable; that many of the 

 streams have disappeared and become mere periodical runs; and that 

 the volume of running water has been considerably reduced ; facts 

 undoubtedly due to the removal of the forests and the cultivation of 

 the soil. 



Prof. Chamberlin, with the active and intelligent aid of Mr. Swe- 

 zey, enters with much detail into the important subject of the distribu- 

 tion of plants over the surface of the state, and accompanies his report 

 with a map representing, as well as can be done, the principal facts as 

 observed and recorded during the progress of the survey. Plants are 

 arranged into fifteen different classes or groups, each of which occu- 

 pies certain localities to the exclusion of the others, and each indicat- 

 ing some peculiarity of soil, geological formation, or climate. 



Under the head of Surface Geology will be found many important 

 facts in regard to the soil and subsoils, of which he distinguishes 

 eight different kinds, each with its peculiar qualities and value. One 

 of these — the calcareous sandy soil, found near Elkhart lake — con- 

 sists mainly of small crystals of dolomite or magnesian limestone, 

 which, while having the appearance of being sandy and unpromising, 

 is found to possess great fertility. 



The measurements along the west shore of Lake Michigan, intend- 

 ed to show the progress that lake is making in wearing away its 

 banks, are not only of interest and importance at the present time, 

 but will possess value to those who shall come after us for many years 

 in the distant future. They show a mean annual abrasion in Racine 

 county of 3.33 feet; and in Milwaukee county of 2.77 feet. The 

 rapidity of geological changes, made under our own eyes, is promi- 

 nently exhibited in the fact above mentioned of a ravine having been 

 formed near Eacine within the past twenty-eight years, M'hich is half a 

 mile in length, one hundred and twenty feet wide and forty feet deep. 



The ample toj)ographical details, including lists of elevations, will 

 have their iise in all future projects for the construction of canals, 

 railroads, and for many other practical and useful purposes. 



Section two of the act to provide for the geological survey, among 

 other objects and duties, very properly requires observations to be 



