H. W. PfarsoH — Oacillatiom of Sea-krc/. 169 



To this point my discussion has heen general, my object being 

 merely to show the present uncertainties as to our knowledge 

 relating to changes in the sea-level, and to call attention to the 

 fallacies on which the arguments of Playfair and Von Buch were 

 founded. I would now introduce a branch of the same subject not 

 alluded to in the previous argument. It is this : — 



It is admitted by all, that most of the lowlands of the Northern 

 Hemisphere have at some time in the past been submerged to less 

 or greater depth beneath the sea. The evidences of great 

 submergences, such as those discussed by Chambers in his " Ancient 

 Sea Margins," or by Prestwich in his " Traditions of the Flood," 

 or as shown by McGee in his " The Lafayette Formation," will not 

 now be considered. To these submergences we are as yet unable 

 to assign a date. I would study, then, those minor relative changes 

 in sea and land, both of depression and elevation, that have occurred 

 since historic times, changes upon which a date and the approximate 

 amount of movement can be fixed, with the object of determining 

 whether these upheavals and submergences show any evidence of 

 being periodic in their nature. We may attribute these changes 

 either to movement in the earth or to movement in the sea, it is 

 immaterial which ; the only question is, have these oscillations 

 shown regular cycles in their occurrence. 



If some period could be discovered which governed these minor 

 changes, it would seem that the law controlling this period might 

 be found, and the establishment of law, if such existed, and the 

 consequent elimination of chance, might enable us to determine with 

 more certainty than at present whether the actual responsibility for 

 these recent changes should be placed upon an unstable earth or 

 upon a shifting sea. 



This question of recent periodic oscillations in the sea-level was 

 forced upon me by certain facts, impossible to explain otherwise, 

 derived from many years' study of the raised beaches of the world ; 

 these facts, owing to the nature of this paper, I cannot now set 

 forth, but they assured me in the strongest manner that a regular 

 <:yde had existed at the time these raised beaches were formed, and that 

 its present existence was almost a certainty. I therefore commenced 

 search for this periodical vibration of the oceanic surface in the 

 records of history and tradition, in the ancient cities of the old 

 world, in the registered changes in the coastlines of all countries, 

 including the American coasts since the time of Columbus. 



The data thus collected are almost unanimous in tlieir testimony ; 

 they point unerringly to a vibration period in the soa-level of about 

 €40 years, an interval of about 320 years existing between periods 

 •of high and of low water. 



The data inform us as well that at periods of high-water tlie 

 submergence increased in amount going north ; they tell us that at 

 previous periods of low-water the sea stood lower than at present ; 

 and finally, they assure us that, following the law of change which 

 has guided these vibrations in the past, we must expect lugher water 

 in the north in the immediate future. This raised sea-level m tho 



