174 GROVE KARL GILBERT— DAVIS [Memoibs [ vol. i xxi i ' > 



before the work was begun and the selection of authors for essays on each of the chief divisions 

 of the geological time scale; later he had to read and to a certain extent revise the manuscripts 

 submitted, and between the beginning and end he undertook a critical study of the principles 

 that had been till then followed in establishing geological correlations and a careful inquiry 

 into the principles that ought to be followed in the future. At all stages of the work he had 

 much correspondence with authors and advisers, some of whom appear to have wished to 

 follow plans of their own rather than to conform to the plan adopted. The following extracts 

 from letters to Prof. O. C. Marsh may serve as samples of Gilbert's way of treating his problems. 

 The first letter was written August 6, 1889. 



. . . The gentlemen who are considering the correlation of the Tertiaries, by means chiefly of invertebrate 

 faunas, find practicallj' no evidence connecting the classification of the Tertiaries of the great interior with 

 the classification of the Tertiaries of the Atlantic and Gulf coasts, the difficulty arising from the fact that 

 the interior Tertiaries are freshwater, while the coastal Tertiaries are marine, so that there is no overlapping of 

 invertebrate faunas. I am informed by Mr. Ward that no light is thrown by the existing collections of plant 

 remains, because the floras obtained from the marine Tertiary formations are very meager. I now write to 

 inquire whether the vertebrates afford data for the discussion of the ages of the individual formations of the 

 coast as compared with the ages of the individual formations of the interior. Between Cretaceous and Post- 

 Pliocene (exclusive) are there common forms from the marine beds of one region and from the freshwater of 

 the other, and if so, are these sufficiently numerous to form a satisfactory basis for discussing the comparative 

 chronology of the stratigraphic columns? 



In connection with his reply to this letter, Marsh appears to have made some unacceptable 

 proposals regarding the introduction of new studies, which brought forth, on December 11, 1889, 

 the following rejoinder from Gilbert: 



I regard it as altogether impracticable to include in such review any unpublished material, except such 

 personal information as may serve to connect the description of species with data in regard to localities and 

 formations omitted or concealed by the paleontologist. " If unpublished material is included, there seems no 

 place to stop, and the undertaking becomes interminable and impracticable. The question to be answered is 

 not what can be shown by vertebrate fossils, but what has been shown, and what is the comparative value of 

 the showing. 



The words " omitted or concealed by the paleontologist " recall the extraordinary state of 

 affairs that had existed in earlier years among rival hunters of fossil "big game" in the Tertiary 

 formations of the West. 



Official correspondence and reports exhibit one phase of Gilbert's work; personal letters 

 exhibit another phase. When the correlation papers had reached an advanced stage in Feb- 

 ruary, 1891, they combined with other duties to reduce the chief geologist, through the winter 

 at least, to the position of an editorial critic. He wrote to a friend: 



My daily grind just now includes the reading of long manuscripts prepared for the printer. For years the 

 Survey has been preparing a series of essays on the formations of the different periods and the means of correlating 

 those of different districts and countries. The direction of this work has been in my hands and now the results 

 are coming in. I have already read piles of MSS. with a total depth of 8 or ten inches and as much more is in 

 sight with early prospect of still a foot or two more. To this I give my forenoons, with my feet comfortably 

 stretched over a chair toward my sitting room fire, and then in the afternoon I sit at my desk, in front of a 

 grinning ink-stained skull, and dictate letters and answer questions. Sunday is apparently a cross between the 

 two occupations, for my feet are up and I am busy with letters at my desk. 



The results of this " daily grind" on the part of the editor, following the labors of his asso- 

 ciates, was a series of bulletins of great practical value to American geological science. The 

 principles involved in correlation were summarized in a paper presented by Gilbert to the 

 International Geological Congress at Washington in 1891, 4 which deserves careful reading by 

 those who have to do with that branch of geological science. 



THE SMALLER DUTIES OF A CHIEF GEOLOGIST 



There can be no question that many of the plans and decisions regarding the geological 

 work of the survey which Gilbert was called upon to make were of large importance in the 

 progress of American science; and it may be well believed that, although his work was varied 



1 Congr. geol. internat., 1891, 151-155. 



