NORTH AMERICAN GEOLOGY FOR 1886. 



By Nelson H. Darton. 



INTRODUCTORY. 



The preparation of this review was undertaken by the writer with 

 serious misgivings as to his ability either to complete it in the time al- 

 lotted, or to reduce the results of a year's activity iu the various branches 

 of g'eologic research to the space assigned ; and the outcome is in sev- 

 eral respects unsatisfactory. 



It was originally intended to include a bibliography of North Amer- 

 ican geology for the year 188G ; but as the work progressed, this was 

 found to be impossible without greatly exceeding the space assigned 

 to the review. It was, however, believed that the bibliography would 

 be of fcuch value to the geologists of this and other countries as to war- 

 rant its separate publication. Accordingly, it was annotated, so mod- 

 ified as to include a subject-index under the same alphabetic arrange- 

 ment as the author's bibliography, and so extended as to become ex- 

 haustive for North America; and thus modified it will form Bulletin No. 

 44 of the U. S. Geological Survey. 



It was originally intended, also, to include in this review a resume of 

 the foreign contributions of the year to geologic philosophy; but this, 

 too, finally i^roved iuipracticable, partly on account of the inaccessibil- 

 ity of much of the literature, and partly on account of the limits of 

 space and time. 



By reason of hurried jireparatiou, the abstracts in this review arc 

 often less full than seen)s desirable, and by reason of the character of 

 the material the abstracts are generally ijresented more or less discon- 

 nectedly. It is believed, however, that all important publications dis- 

 tributed during 188G, or bearing that date and received early in the 

 present year, are noticed in the following pages. With the exception 

 of a few words of introduction or conuection, the writer has acted sim- 

 ply as an abstractor, and has endeavored to avoid bias or partiality. 



QUATERNARY. 



1. No subject in American geology is now receiving more attention 

 than that including the many interesting problems of the Quaternary. 

 Each year brings forth a considerable mass of literature in which con- 



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