G. K. Gilbert — Congress of Geologists. 433 



tion of terrane, a word whose English meaning has not been 

 well established.* 



The fixation of the chronologic terms creates a similar dif- 

 ficulty. We have crystallized out of our magma the terms era, 

 period, epoch and age, and there remain in the ground-mass only 

 eon, cycle and time. Of these, eon has a poetic connotation which 

 seems to unfit it for this particular use; cycle implies repetition 

 or recurrence; and time has been so generally applied to un- 

 limited duration that it is difficult to apply it also to limited 

 duration, even though the nature of the limitation be indefinite. 

 On the whole, time seems open to the least objection, but I can- 

 not help regretting that either period or age, both of which have 

 heretofore passed current in the indefinite sense, was not reserved 

 by the congress for that function. With English-speaking peo- 

 ples the word eon could have been better spared for the definite 

 series. 



But while the terms selected by the congress are not beyond 

 criticism, the benefits to be derived from an agreement in an 

 orderly system are so great that I for one shall unhesitatingly 

 adopt them as they stand, — provided, of course, that the con- 

 gress makes no effort to improve its selection. f A small reform 

 of this nature yields its profit to this as well as future genera- 

 tions, and I hold it a duty to favor even those reforms which 

 involve so much effort and pains that their blessings cannot be 

 realized by those who initiate them. Such are the exchange of 

 our English spelling for a rational system, and the exchange of 

 decimal notation in arithmetic for a binary notation. My ap- 

 plication of the new nomenclature begins with this address, in 

 the preparation of which I have experienced its utility. That 

 you may have no difficulty in interpreting my reformed lan- 

 guage, I have placed the taxonomic legend on the wall, with 

 the addition of the complementary indefinite terms, terrane and 

 time. 



m Group. Era. 



& System. Period. $ 



£ Series. Epoch. .5 



£ Stage. Age. ^ 



There are propositions before the congress to distinguish the 

 names of individual groups, systems, series and stages by means 



* In a review of this paper, by Dr. Persifor Frazer, it is pointed out that this 

 suggestion is not original with me, having been made by Prof. Eenevier, at the 

 Berlin meeting of the Congress, and that terrane is used in this sense in the 

 pamphlet published by the American committee. The review, which consists 

 chiefly of unfavorable criticism, may be found in the American Naturalist for 

 September— vol. xxi, pp. 841-84*7. 



f Several national committees favor the interchange of the words group and 

 s tries. 



