PREFACE. 



This volume, the first of the final volumes of the geological and natural 

 history survey of Minnesota, needs but few words of introduction. It was 

 with much trepidation, but with unreserved devotion to the work, that the 

 writer began alone, in October, 1872, the geological survey of the state of 

 Minnesota. The fund allowed by the Legislature was one thousand dollars 

 per year, to cover all expenses. This sum was doubled by the next Legisla- 

 ture, and the salt spring lands of the state were placed in the hands of the 

 board of regents to defray the expenses of the survey. One half of each 

 year, up to 1S7S, was given to instruction in the University. The field- 

 work of the summer vacation was described in an annual report, hurriedly 

 prepared in the autumn and early winter of each year. In 1878 the regents 

 made other provision for the work of instruction. In 1879, Mr. Warren 

 Upham was employed, and he has remained an assistant on the survey up 

 to the present time. 



Although the period of ten years is covered by this volume, it does not 

 embrace all the results of the work of that length of time. In accordance 

 with the general law of the survey, several other departments have been 

 prosecuted. The series of annual reports has been maintained, the General 

 Museum has been established, and investigations of the palaeontology and 

 mineralogy of the state initiated. In general the design has been to plan 

 the work systematically and execute it thoroughly, based upon an ex- 

 pectation of final completion. This of course finds, at this time, many 

 lines of investigation still open, and much field-observation still unclassified. 



The aim in this volume has been to state facts rather than conclusions. 

 Whenever an attempt has been made to assign a cause to phenomena, it 

 has been so evidently the cause, in the light of the facts stated or univer- 

 sally admitted, that the description of the phenomena would be incomplete 



