May 3, 1907] 



SCIENCE 



703 



deposits, containing marine fossils, is be- 

 lieved to be locally superposed upon the fresh- 

 water or brackish-water sands and clays of the 

 delta and marsh reentrants. The base-line of 

 the scarps, the surface of the delta plains, and 

 the inner border of the marine terrace are all 

 ■closely at the same level. The scarps rise 

 sharply above their base line, and gain a 

 height dependent on the altitude of the head- 

 land in which they were cut; the terraces 

 slope very gently waterward, their layers 

 resting unconformably on the submerged and 

 eroded land-surface, and their composition and 

 thickness presumably varying with local 

 changes of depth, waves and currents. 



It is the occurrence, at various altitudes 

 above sea-level, of features similar to those of 

 the present shore line, but now more or less 

 wasted by erosion, that has led Shattuck to 

 bis ingenious interpretation of the Sunder- 

 land, Wicomico and Talbot terraces. He 

 traversed the coastal plain in all directions, 

 but not until it occurred to him to explain 

 its details of form and structure by means of 

 marine action at several levels was it possible 

 to bring order out of confusion. The scarps, 

 especially the higher earlier ones, are dulled 

 by weathering; and the terrace fronts are 

 dissected by retrogressive streams, especially 

 where undercut by the next lower scarp. 

 Nevertheless they are still traceable. It is 

 significant that the correlation of the different 

 parts of each terrace is usually not based on 

 paleontological evidence, for most of the de- 

 posits do not bear fossils; nor on diversity of 

 composition, for the materials of the succes- 

 sive terraces are all much alike in their vari- 

 able nature; but chiefly on the continuity and 

 similarity of surface, form and deposits, when 

 traced horizontally in various districts ; and 

 on the systematic sequence of forms and 

 deposits, when followed down from higher to 

 lower levels. The plane, marked by the inner 

 border of each terrace, must have been hori- 

 zontal when formed, and is now faintly 

 inclined to the southeast, as a result of slight 

 inequality in later elevatory movements. 

 The Talbot terrace, next preceding the pres- 

 ent, has still a practically level inner border; 

 the Sunderland terrace, having felt all the 



later changes of level, summarizes their in- 

 equality in a seaward slope of about three feet 

 to a mile. Much more distinct than these 

 extremely faint slopes is the manifest though 

 still gentle descent of each terrace as it de- 

 parts from its inner border at the scarp base 

 towards the larger valleys with which it is 

 related. 



The maps that are bound in with the report 

 give it excellent illustration. First is a gen- 

 eral map of eastern Maryland (1,500,000), 

 showing all the formations here described; 

 and from this it appears clearly that, if the 

 Lafayette and Sunderland ever existed (as 

 they probably did) on the eastern peninsula 

 of Maryland and Delaware — the ' Eastern 

 Shore ' — they were removed by successive at- 

 tacks of subaerial and marine erosion, thus 

 allowing the Wicomico terrace to spead over 

 the axial upland of the peninsula as a broad 

 plain, as yet but little dissected over its medial 

 area. It is only on the group of dissected 

 peninsulas between the Chesapeake and Poto- 

 mac that the whole series of formations can be 

 found, descending step-like from Lafayette on 

 the uplands to Eecent at the shore line. The 

 inferred relations of land and water at suc- 

 cessive epochs are even more clearly shown 

 on a series of four smaller maps (20 miles to 

 an inch), illustrating the supposed areas of 

 submergence in Lafayette and later times. A 

 final map indicates the inferred emergence of 

 the land and the extended rivers of the Talbot- 

 Eecent interval of uplift. Numerous plates 

 give views of the terrace deposits and of the 

 scarps, recent and abandoned. 



A brief review of certain points, on which 

 this excellent report is not altogether clear at 

 first reading, may now be presented. 



1. As to the stage of erosion of the Cre- 

 taceous-Tertiary coastal plain, that had been 

 reached when depression occurred and the 

 deposition of the Lafayette commenced. It 

 is said that " there was a long interval of ero- 

 sion before deposition of the Lafayette beds 

 began" (p. T8), and that "the Lafayette was 

 developed as a plain surface sloping gently 

 toward the surrounding waters " (p. 123) ; but 

 the stage of erosion reached in pre-Lafayette 

 time is not explicitly stated in physiographic 



