66 CHANGES OF LEVEL 



true changes of level is the alteration of the coast-line due to the 

 washing away of land by the sea, causing the latter to advance, or, 

 on the other hand, to the silting up of shallow water by the depo- 

 sition of sand or mud, which makes the land advance at the ex- 

 pense of the sea. 



The evidences of elevation along any coast-line may be more 

 easily made out than those of depression, because when land 

 comes up out of the sea, the traces of marine action upon its 

 surface are always present in one form or another. When, on the 

 contrary, land goes down beneath the sea or the sea rises over 

 the land, the old land surface is speedily changed and buried out 

 of sight. 



Evidences of Elevation. — Along coasts which have been inhab- 

 ited for many centuries by civilized man, ancient structures, like 

 quays and bridges, which were built in the water may now be 

 found high above it. Such changes have been noted in the lands 

 which adjoin the Mediterranean, especially in southern Italy and 

 the island of Crete. The temple of Jupiter Serapis at Puzzuoli, 

 near Naples, is a classic example of this. In this building thiee 

 marble columns are still standing, and on each of them is a belt, 

 about ten feet above the ground and nine feet wide, honey-combed 

 by the boring mollusc, Lithodomus, which still lives in the neigh- 

 bouring bay. Evidently the temple was first submerged, and when 

 under water the columns were attacked by the mollusc, and after- 

 wards it was upheaved, but is now sinking once more. 



Rocks and cliffs long exposed to the action of the surf are worn 

 and marked in a characteristic fashion, and when found far above 

 where the surf can now reach them, are evidences of upheaval at 

 that point. Such well-defined sea-marks high above sea-level are 

 common in the high latitudes of the northern hemisphere, and the 

 change is still in progress in many places. The Scandinavian 

 peninsula shows slow changes of level, though not everywhere the 

 same ; south of Stockholm there is a slight subsidence, north of that 

 point there is a rise, which increases northward, and at the North 

 Cape is believed to average five or six feet per century. These 

 results have been much questioned, but after a renewed examina- 



