academy of SC.E.NCBS] FIELD WORK IN COLORADO 211 



of facts." 6 Much later he invented the convenient term, "rock-feet," to serve as a unit for the 

 measurement of a local excess or defect of gravity, 6 and at about the same time he coined the 

 word, "isobase," to designate a particular kind of contour line, 7 and proposed to use the word, 

 "discreet," with a meaning to which he had long wished to give a name. 8 A few years later 

 he took issue with a geologist who deprecated the introduction of new terms into scientific 

 usage; ° and in a presidential address of 1909 he employed the novel term, "malloseismic," 

 without apology but with explanation. That he recognized the helpfulness of technical terms 

 was moreover shown by the care he took in the proper use of those which he adopted; on one 

 occasion he wrote critically to a correspondent regarding the proper use of the words drumlin 

 and drumloid, recommending that " the name drumlin should be applied to the species, including 

 all varieties, and that drumloid will do best service as an adjective to be applied to things that 

 resemble drumlins in any one of many ways. . . . The restriction of the word drumlin to a 

 variety, and the assignment of drumloid to another variety, not only spoils a good adjective 

 but breaks up one of the best defined species in the morphology and taxonomy of the drift." 



More significant still is the emphasis that Gilbert placed, in his tribute to Powell at a 

 memorial meeting held in Washington in 1904, on the importance of "classification" as a part 

 of his chief's work in science, along with "observation, explanation, and application to welfare," 

 and especially on the value of the ideas that are embodied in Powell's three river terms. They 

 "fell on fertile ground, and have had a marvellous development. . . . Geologists and geog- 

 raphers now recognize that each hill, hollow, and plain of the earth's surface originated by some 

 process of change and is therefore susceptible of explanation and interpretation. Whereas 

 geological history was formerly read in the rocks alone, it is now read not only in the rocks 

 but in the forms of the land and in the arrangement of the streams." It is, however, not 

 simply Powell's ideas that have prevailed, but also the terms in which the ideas were embodied; 

 and it would therefore seem that if, after the three kinds of streams and valleys then known 

 had been named, a fourth kind was fouDd, as unlike each of the three as they are unlike one 

 another, it also should have been given a name; and it is all the more regrettable that no fourth 

 name was proposed when one recalls that the qualifying adjective, "subsequent," which goes 

 so well with consequent, had been used by Jukes as long before as in 1862 to indicate that, as 

 already told, the retrogressive erosion of longitudinal streams along belts of weak structure 

 takes place as a sequence to the downward erosion of the transverse rivers which such streams 

 join. It may be fairly urged that streams of this class are as different from consequent, ante- 

 cedent, and superimposed streams as laccoliths are unlike dikes, necks, and sills. Why Gilbert 

 left such streams without a name is a puzzle. It surely can not be that the absence of a technical 

 name for the fourth class of streams is due, not to its noninvention, but to its having been held 

 back by the editorial net through the meshes of which the folio texts are very properly strained, 

 for the texts of various folios include, and with entire propriety, such terms as syncline, pale- 

 ozoic, unconformity, and metamorphism; freibei'gite, microperthite, chalcopyrite, and pyrar- 

 gyrite; Brachyphyllum, Widdringtonites, Ctenopteris, and Onychiopsis; to say nothing of 

 granodiorite, metadiabase, augite-grano-cecilose, and biotite-hornblende-grano-bandose; all of 

 which illustrate the keen pursuit by which various kinds of facts are traced, captured, classed, 

 and labeled. In the presence of a multitude of admitted terms represented by the few just 

 cited, it does not seem that a technical name for a fourth kind of streams and for the valleys 

 which such streams drain would be a heavy additional burden for the folios to bear. Indeed, 

 had Gilbert sanctioned such a name, it would surely have passed through the meshes of the 

 editorial net and it might now have gained as acceptable a place as syncline, metamorphism, 

 and the rest; and precisely as those terms compactly replace long paraphrases, so the needed 

 stream name might have replaced in certain Appalachian folios such paraphrases as "longi- 

 tudinal courses on the long narrow outcrops of the easily eroded limestone," and "lesser valleys 

 along the outcrops of the softer rocks." 



1 Amer. Journ. Sci., lii, 1S78, 94. < Science, vii, 1898, 94. 



6 Bull. Phil. Soc. Wash., xiii, 1895, 69. » Science, jcii, 1905, 28-29. 



» U. S. Qeol. Survey, 18th Ann. Rept, 1898, 604. 



