Geology and Mineralogy. 401 



have been able to detect only a very minute quantity of magnesia 

 in any specimens I have tried, but much alumina." Thereupon 

 he, with good reason, called the rock " very fine-grained mica 

 slate." But the other geologists, including Emmons and Hitch- 

 cock, did not accept of his determination, and the error continued 

 in the science of both America and Europe, for forty years and 

 more. Dr. Dewey was a keen-eyed student of Nature, and New 

 England geological science lost much by his leaving the field 

 after having well passed its threshold. 



Professor Ebenezer Emmons received his scientific inspiration 

 from Professor Eaton, whose rousing lectures, at Williams Col- 

 lege, he heard while in his Junior year. Under its influence he 

 became one of the most active and faithful geologists of the 

 country. He was a pupil in Professor Eaton's Rensselaer school, 

 which was opened in Troy in 1824, and in 1826, the year of his 

 graduation, published a small "Manual of Mineralogy and Geol- 

 ogy," for the Rensselaer school. (This Manual was my first 

 school book on the science while at a High-school in Utica, 

 between the years 182V and 1830, where another Rensselaer 

 school graduate was our instructor in chemistry and natural his- 

 tory.) Like Professor Dewey he became an instructor in Will- 

 iams College, entering upon his duties there, as a Professor of 

 Natural History, in 1833, and then commenced his geological 

 investigations. 



6. Fifth Annual Report of the U. S. Geological Survey, 1883 

 to 1884; by J. W. Powell, Director. 470 pp. roy. 8vo, with 

 many plates and other illustrations. — The report of the director, 

 here presented, shows that a large amount of geological work is in 

 progress under the survey and that all of it is of high order. 

 The papers published with the report are the following : The 

 topographical features of Lake shores, by G. K. Gilbert ; Prelim- 

 inary paper on an investigation of the Archaean formations of the 

 Northwestern States by R. D. Irving; The requisite and qualify- 

 ing conditions of Artesian wells, by T. C. Chamberlin ; The 

 gigantic mammals of the order Dinocerata, by O. C. Marsh ; 

 existing glaciers of the United States, by I. C. Russell; and 

 a Sketch of Paleobotany, by L. F. Ward. The work of Profes- 

 sor Marsh on the Dinocerata has already been noticed at length 

 in vol. xix (1885) of this Journal, and the report of Mr. Russell 

 briefly in the current volume ; and Professor Irving has a paper 

 in vol. xix on the Archaean which bears on some of the points he 

 here considers. 



Professor Chamberlin's report, as its title implies, is a scientific 

 review of the conditions favorable and unfavorable to success in 

 Artesian borings, and has a direct reference to economical results. 

 The discussion is based on a wide range of facts from a geologi- 

 cal source and from past experiences in borings, and the explana- 

 tions are accompanied by many illustrating figures. The report 

 is therefore an excellent manual on the subject. 



A new feature in artesian boring came to the writer's knowl- 



Am. Jour. Sci — Third Series. Vol. XXXI, No. 185. — May, 1886. 

 25a 



