706 



SCIENCE 



[N. S. Vol. XXV. No. 644 



admirably analyzed and illustrated. It is true 

 that by no means all of the deposits which are 

 treated as of marine origin are known to eon- 

 tain marine fossils; yet the localities where 

 marine fossils have been found in them are 

 held to be of demonstrating value for many 

 others. With all these points in mind, one 

 may picture very clearly the rapid succession 

 of short-lived events during the Sunderland 

 depression and the later oscillations. The ad- 

 vancing Sunderland sea presumably shaved off 

 a film from the sinking surface ; and the thick- 

 ness of the film increased to a measure of fifty 

 or more feet when the greatest encroachment 

 of sea on land was made during the pause 

 which closed the depression. In the following 

 partial emergence, the sea presumably with- 

 drew without doing recognizable erosive work 

 — much in the way that the tool of a planing 

 machine backs harmlessly across an iron plate, 

 preparatory to taking ofi a shaving in its next 

 advance. But the extended streams and rivers 

 took advantage of the withdrawal of the sea 

 and eroded new valleys in the margins of the 

 revealed terraces. The advances of the sea in 

 Wicomico and Talbot times repeated the op- 

 erations of the Sunderland advance; and the 

 recent advance, now in operation, gives the 

 key to its predecessors. 



The paleontological pages of the report show 

 that the terraced coastal plain was a forested 

 region during the time of its oscillations, with 

 many trees like those of to-day; and that 

 mammoths and elephants were among its in- 

 habitants. Nearly all the marine forms are 

 found living along the present coast.' 



Although this report is elaborated far be- 

 yond any previous descriptions of the Mary- 

 land coastal plain, there are certain features 

 to which detailed studies may still be profit- 

 ably directed in the future. There is, of 

 course, a continual watch to be kept for new 

 localities where sections of the various ter- 

 races may be exposed, and particularly where 

 fossils may be found. All such discoveries 

 will have high value in testing the correctness 

 of the conclusions now set forth, inasmuch as 

 the capacity of a theory reasonably to account 

 for facts of later discovery is one of its best 



recommendations. Moreover, there are cer- 

 tain physiographic details to be filled in, which 

 will give increased verisimilitude to the pic- 

 tures of the Maryland Pleistocene already 

 drawn. These details have regard to the con- 

 trasts that may be expected between the shore 

 lines of the exposed ocean front and of the 

 protected bay borders. For example : in Sun- 

 derland time, the peninsula of the Eastern 

 Shore was completely submerged; the western 

 border of what is now Chesapeake bay must 

 then have been beaten with breakers from the 

 ocean swell — except in so far as the swell was 

 expended in passing over the shoals of the 

 submerged Eastern Shore. The Sunderland 

 scarp thus formed should have a different out- 

 line from the Wicomico, Talbot and Eecent 

 scarps, lower down the west Chesapeake slope;, 

 for when the latter scarps were formed, Chesa- 

 peake bay was enclosed from the ocean by the 

 Eastern Shore peninsula, and its limited waves- 

 could not have trimmed a shore line of the 

 same expression as that made by the ocean 

 breakers. Similarly, the Talbot scarp cut in 

 the Wicomico terrace on the eastern side of 

 the Eastern Shore must have been cut by 

 ocean breakers similar in force to those which 

 have in Eecent time formed the long, smooth- 

 curved, off-shore sand reef by which Chinco- 

 teague and other ' bays ' are enclosed along' 

 the present ocean front. Hence a similar off- 

 shore sand reef might have been formed in a 

 similar situation during the Talbot epoch. As- 

 no such Talbot sand reef is described, the 

 reader is left somewhat in doubt as to whether 

 it is really absent or whether exploration on 

 the farther (eastern) slope of the Eastern 

 Shore was not carried out in sufficient detail 

 to determine it. Again, it is noted that the 

 scarp and terrace of one epoch are occasionally 

 undercut and entirely destroyed by the under- 

 cutting of the scarp of the next succeeding 

 epoch ; just as might be expected if the general- 

 slope of the attacked surface had been some- 

 what steeper in the later than in the earlier 

 epoch. It will be interesting to learn if inde- 

 pendent evidence is eventually found to show 

 that such was the case. Finally, there are 

 certain local features of special significance 



