PREFACE ix 



Pierce, who has draughted the diagrams. Though credit has in 

 most cases been given where illustrations have been made from 

 another's photographs, yet especial mention should here be made 

 of the debt to Dr. H. W. Fairbanks of Berkeley, California, whose 

 beautiful and instructive photographs are reproduced upon many 

 a page. 



As given at the University of Michigan, the lectures reflected 

 in the present volume are supplemented by excursions and by so 

 much laboratory practice as is necessary to become familiar with the 

 more common minerals and rocks, and to read intelligently the usual 

 topographical and geological maps. In the appendices the means 

 for carrying out such studies, in part with newly devised apparatus, 

 have been indicated. 



The scope of the book precludes the possibility of furnishing the 

 reader with the sources for the body of fact and theory which is 

 presented, although much may be inferred from the names which 

 appear beneath the illustrations, and more definite knowledge will 

 be found in the references to literature supplied at the ends of 

 chapters. A large amount of original and unpublished material 

 is for a similar reason unlabeled, and it has been left for the pro- 

 fessional geologist to detect these new strands which have been 



drawn into the web. 



WILLIAM HERBERT HOBBS. 

 ANN ARBOR, MICHIGAN, 

 October 25, 1911. 



