MARYLAND GEOLOGICAL SURVEY 109 



but as ages passed the less conspicuous portions would gradually yield to 

 the Leveling inlluences of erosion, such as soil creep, plant roots, culti- 

 vation, etc., and might finally disappear altogether. Tilting might 

 change the original attitude of the surface while erosion would also de- 

 stroy in a large measure the continuity of the formation, but as long as 

 portions of it remained, the old surface could be reconstructed and its 

 history determined. At the margin of this terrace the waves of the ocean 

 and estuaries would begin their attack. They would quickly fashion a 

 wave-cut cliff around its border and beneath this build up a subaqueous 

 platform which would grow in width in proportion as the waves en- 

 croached on the land. If this in turn were elevated, it would form an- 

 other terrace having the same characteristics as its predecessor, but would 

 show its individuality in age and formation by lying beneath it, by being 

 separated from it by a scarp-line more or less continuous, and by having 

 its surface less dissected by erosion. At its base once more the waves 

 would cut another scarp-line and build another terrace which in time 

 might be raised to form another member of the series. These terraces, 

 although subsequently dissected and separated one from another by ero- 

 sion, could still be distinguished by sequence in topographic position. 

 Eegional tilting, which might occur from time to time, would leave its 

 mark in differences in attitude among the terraces themselves. The high- 

 est, being the oldest, would accumulate the movements and its position 

 would be a composite of them all. The others would record successively 

 less deformation in proportion as they were younger until in the plat- 

 form building beneath the waves of the estuaries, only the latest earth 

 movements would find expression. 



If the essential features of the Recent terrace are now clearly under- 

 stood, it will be a simple matter to show how " continuity of deposits," 

 " similarity of topographic form," and " sequence in topographic posi- 

 tion " may be applied in discriminating the relative ages of the earlier 

 formations. It may not he amiss, however, to say in this connection that 

 before, and even after, the author had begun to apply these methods of 

 interpretation, a large number of alternative hypotheses were considered 

 and rejected as inadequate. As the history of an investigation is not 



