156 PROCEEDINGS OF THE AMERICAN ACADEMY. 



tion of the last century, it does not follow, from such observations 'per se, 

 that the land has moved in that same direction for any length of time 

 previous to the earliest of said observations ; and moreover, if in addition 

 to such demonstrated recent movement there exists geologic or geographic 

 evidence to show earlier motion in the same direction, such cumulative 

 evidence of motion in one direction is no valid argument for continued 

 motion in the same direction, for any period of time longer than that re- 

 quired by the nature of the evidence itself The converse of this propo- 

 sition is also true, viz. that evidence which shows that a country has 

 been raised or sunken does not prove that the region has been rising or 

 sinking in recent time, or is to-day rising or sinking. 



That the time element has been left out of the majority of previous 

 considerations of shorelines, in the discussion of their elevation or depres- 

 sion, will be clearly perceived by any one who vs^ill go over the literature 

 of the subject. 



Areas of Elevation and Depression as Mapped. — A comparison of 

 three maps of " rising " and "sinking" regions will show how different 

 points of view have led to opposite conchisions. Dr. G. R. Credner 

 considers the presence of large deltas a proof of slow rising, therefore in 

 his map of changes of level * he regards all regions of great deltas as 

 rising. In contrast with Credner's map, compare. that of upheavals and 

 depressions by Reclus.f In this map, " drawn after Chas. Darwin," all 

 regions where the coral growth is prevailingly of the atoll and barrier 

 reef type are given as sinking, while those regions where the fringing 

 reefs occur are mapped as regions of upheaval. Thus the hypothesis 

 of Darwin, t who regarded the form of coral construction as evidence of 

 " probable subsidence " and " probable elevation," when given such defi- 

 niteness as upon the map of Reclus, makes a striking contrast to the map 

 by Dr. Credner; many "rising areas" on the one are "sinking areas'"' 

 upon the other. Neither of these two criteria can be safely used to show 

 present or recent movement, nor are they more than hypothetical sug- 

 gestions of earlier changes of level. 



Scandinavia on both of these maps is given as rising, because of its 

 raised beaches and " water-marks." This peninsula, as will be shown 

 later, is in the larger geographic sense in a cycle of development follow- 

 ing depression. 



An interesting historico-geographic study could be made by a com- 



* Pet. Geog. Mitt., Erg. Nr. 56, 1878, Tom. III. 



t La Terre, 1872, I. 702, PI. XXIV. 



t The Structure and Distribution of Coral Reefs, 3d ed., 1889, PI. III. 



