4 Barrell — Movements of the Strand Line 



each descending series, destroyed and covered up while we 

 watched by the following ascending series. The tide and 

 storm might meanwhile be rising higher, and j 7 et the writing 

 of the past would appear as of a subsiding nature. The lesson 

 to be drawn is that the record of a descending series measures 

 only the descending sequence from the last maxima of the 

 greater rhythms. It does not in itself tell the present trend of 

 the oscillations. 



Since the end of the Oligocene the strand has, on the whole, 

 been retreating, the continents rising higher, the climates grow- 

 ing colder. There seems, in the Pleistocene, to have been a cul- 

 mination of crustal and climatic oscillations, closed by a 

 descending series. Men have taken hope that the ice age is 

 past and have looked upon the Quaternary revolution as clos- 

 ing. But the study of the rhythm of the waves robs us of that 

 assurance. At several times in the Pleistocene that view, as 

 based upon apparent subsidences of crustal and climatic move- 

 ments, would have been far better justified by the evidence 

 than it is at the present moment. The high latitudes, unlike 

 their state through the most of geologic time, are still mantled 

 with glaciers. The shore lines are now in a stage of earliest 

 youth. We live in fact within the Age of Ice, within an age 

 of crustal unrest and revolution ; the geologic morrow may 

 bring forth greater and more compelling changes than the 

 geologic yesterday. With this understanding of the nature of 

 composite rhythms, always seen in retrospect as ending with a 

 descending series, we should study the record of the ocean 

 waves made on " Time's great continental strand." 



Indications of Oscillations given by Subaqueous Profiles. 



The first line of investigation which led the writer to an in- 

 tersection with the problem of recent strand-line movements 

 was in a study of present shore action as a basis for the 

 development of " Some Distinctions Between Marine and Ter- 

 restrial Conglomerates."* The pressure of other work and the 

 desirability of making quantitative measurements has pre- 

 vented the publication of more than an abstract of this article, 

 which led up to the conclusion that " the truly terrestrial 

 forces produce vastly more gravel, spread it far more widely, 

 and provide more opportunities for deposition than do the 

 forces of the littoral zone." This conclusion was reached by a 

 re-examination of the data used by Geikie, de Lapparent, and 

 Penck for determining the relative rates of erosion. The 

 result was to diminish still further the ratio of marine to ter- 

 restrial erosion as given by those authors. It was estimated, 

 by multiplying the length of shore line by the thickness 



* Abstract, Bull. Geol. Soc. Am., vol. xx, p. 620, 1908. 



