H. W. Peanon— Oscillations of Sca-kvel. 107 



V. — Oscillations in the Sea-level. (Pakt I.) 



By H. W. Pearson. 



(PLATE IX.) 



WHEN man first began the study of the earth's surface, he 

 encountered at the very beginning, along the borders of the 

 sea-coasts, on the lowland plains, and even on the hills, certain 

 puzzling phenomena, difficult of explanation. These perplexing 

 observations seemed to testify, by means of ancient raised beaches, 

 fossil oyster and mussel shells, dessicated salt marshes, fragments 

 of wrecks, and even by ancient anchors in the hills, that at some 

 unknown time in the past the sea had " formerl}' been where the 

 land now was." 



Straton of Lampsacus and Eratosthenes (between 200 and 300 b.c.) 

 explained these facts by supposing that the Mediterranean and the 

 Euxine had once been dammed by barriers at the Pillars of Hercules 

 and at Byzantium, and that hy the breaking down of these barriers 

 "much that was formerly covered by water had been left dry." 



Strabo (54: is.c. to 24 a.d.), holding Straton and Eratosthenes to be 

 in error, insisted that explanations of these facts must be found 

 either in inundations caused by upheavals of the sea bottom, or iu 

 actual subsidence of these lands beneath the level of the waters and 

 their subsequent upheaval, his preference being given to the first- 

 named cause, as he deemed that the humidity of the bottom would 

 render it more liable to shifting. 



Here was raised, iu the early morning of scientific investigation, 

 the greatest problem of geology, or of geography, and such little 

 progress has been made in the settlement of this question during the 

 two thousand years that have since passed over our heads, that 

 to-day if it is asked, are these evidences of former submergence and 

 upheaval due to changes in the sea-level itself, or are they due to 

 movements in the crust of tlie earth, no man can make certain reply. 



That this uncertainty has real existence can be seen from the 

 examples of opposing opinions herein quoted. 



Celsius in 1730, in explanation of the apparent upheaval of the 

 Baltic shores, affirmed a variable sea-level. Play fair in 1802 and 

 Von Buch in 1807, adopting the second hypothesis of Strabo, 

 affirmed movement in the earth's crust. 



Sir J. A. Picton contended that the level of the sea had not 

 changed, that it is the land alone which has altered its level 

 (Proc. Liverpool Geol. Soc, vol. vi, p. 38). Sir Charles Lyell 

 insisted " that the level of the ocean was invariable," and that the 

 "Continents are inconstant in their level, as has been demonstrated 

 by the most unequivocal proofs again and again, from the time of 

 Strabo to our own time" ("Principles," 9th ed., Appleton, p. ol8). 

 Le Conte says, " we may look upon the sea-level as fixed 

 ("Elements," p. 138). 



In opposition to these statements of Picton, Lyell, and Le Conte, 

 James Geikie says, " the more recent raised beaches may be hkely 

 enough due to oscillations of the sea-level itself, and not necessarily 

 to movements of the land" (" Pre-historic Europe," p. 525). 



