796 



SCIENCE. 



[N. S. Vol. III. No. 74. 



universities or the establisliment of mone- 

 tary systems. If we wait for them to speak 

 out we must wait indefinitely. If the in- 

 ti-oduction of the metric system be accom- 

 plished in America we must act in the 

 light of experience already acquired in Eu- 

 rope, which is far more vahiable than any 

 amount of theorizing about the apprehended 

 effect upon poorer, classes who have not yet 

 tried it. 



The suggestion that an International Com- 

 mission should be appointed to secure unity 

 of action between the United States and 

 Great Britain is eminently worthy of adop- 

 tion. Any system of metrology adopted 

 by one of these two nations must necessarily 

 be adopted nearly, if not quite, simultan- 

 eously by the other. It is very much to be 

 desired that this proposition shall be 

 brought before Congress as soon as the 

 Committee on Coinage, Weights and Meas- 

 ures is again ready to act. 



W. Le Conte Stevens. 



TWO EROSION EPOCHS— ANOTHER SUG- 

 GESTION. 



Hekshet's recent suggestion (Science, 

 Vol. III., pp. 620-622) that a specific desig- 

 nation be given to the epoch of post-Lafay- 

 ette erosion in the eastern United States is 

 an excellent one. The epoch is one of the 

 most clearly defined in the physical history 

 of the continent ; its record has already 

 been interpreted over a vast area, and a 

 specific designation will tend at once to crys- 

 tallize knowledge and to aid in its diffusion. 

 So the suggestion marks an advance in sys- 

 tematizing American geology. 



To the writer the name selected seems 

 hardly a happy one, partly because 'Ozark' 

 is already in so general use in geologic no- 

 menclature as perhaps to occasion confusion, 

 partly because there is a certain incongru- 

 ity in applj'ing the name of a mountain 

 region to a degradation period ; but this 

 question of fitness in name gives no occa- 



sion for hesitating to adopt the suggestion. 



There is a graver question concerning 

 the age of the epoch. Hershey intimates, 

 without argument, that there is ' general 

 agreement * * * that the post- Lafayette 

 period of erosion is early Quaternary in 

 age ; ' but, so far as the writer is aware, 

 most students have connected the degrada- 

 tion period with the preceding aggradation 

 period — those geologists who have exam- 

 ined the formation and its degradation 

 record (with perhaps two exceptions) re- 

 garding both as pre-Quaternaiy, and those 

 who have written voluminously on the 

 formation without seeing it regarding it as 

 Quaternary. It seems worth while to di- 

 rect attention to this question of age, partly 

 for the purpose of pointing out that there is 

 no less need for the term even if the epoch 

 does not belong to the Pleistocene, and thus 

 to the period so well classified by Cham- 

 berlin ; it is not absolutely necessary to 

 decide whether the Ozarkian epoch be classi- 

 fied as Pleistocene or Neocene, since each 

 student can arrange his pigeon holes and 

 their contents as he pleases, and since in- 

 creasing knowledge is constantly making 

 toward better arrangements ; but it is im- 

 portant that this well-marked erosion epoch 

 should bear a denotive label. It is also im- 

 portant to remember that, if erosion be re- 

 garded as yielding a time measure, the ref- 

 erence of the Ozarkian to the Pleistocene 

 multiplies many times the commonly recog- 

 nized duration of that period. 



Hershey adequately recognizes the extent 

 of the erosion aiFected during the Ozarkian 

 epoch in (a) the Coastal plain of the Atlan- 

 tic and Gulf, and (b) the broad area extend- 

 ing thence to the glacial margin ; but it 

 seems desirable to recognize (hypothetically 

 perhaps, but with constantly' increasing evi- 

 dence), the record of the epoch in (c) the 

 glaciated region : In the Coastal plain this 

 epoch of profound erosion is recorded in es- 

 tuaries hundreds of miles in length and 



