170 S. W. Pearson — Oscillations of Sea-level. 



north should culminate within 200 years, while the advance should 

 be visible within a few decades. 



The points in the curve illustrating the variation in level of the 

 surface of the sea were sought for and found under a system of 

 reasoning adopted after consideration of the results obtained from 

 the investigation of the raised beaches before mentioned. This 

 investigation furnished me certain testimony strongly opposed to all 

 my prepossessions, yet, if I had interpreted the records correctly, 

 I felt compelled to adopt as logical conclusions the following 

 theories : — 



1. Since the carving of these ancient terraces there had been no 

 movement of the earth's crust, but these terraces lay in position 

 exactly as originally traced. 



2. The date of these beaches is unknown, but they certainly 

 antedate the historical period. I must therefore conclude that since 

 the dawn of history no upheaval or subsidence of the earth's crust 

 can have occurred, and explanation of the observed recent sub- 

 mergence and emergence of lands must be sought for in vertical 

 movements of the sea itself, rather than in upheavals or depressions 

 of the crust. 



3. I had reason to strongly suspect, in fact I regarded it as almost 

 certain, that at the time of deposition of these terraces alternate 

 rising and falling of the sea-level had occurred, that the traces of 

 this movement were plainly discernible, that I had good cause to- 

 suspect the present existence of these same cycles of alternate ascent 

 and descent in the sea-level, and that if these oscillations existed they 

 should be uniform in direction of movement over one hemisphere. 



Impressed, then, with the logic of the facts which had led up to 

 these conclusions, facts which are set forth in other papers, I started 

 on a new research, seeking for evidence of these suspected cycles, 

 of the approximate dates of their maxima and minima, and of the 

 amount in feet of their vertical vibration. 



The apparent absurdity of entering upon such a labour as this is 

 manifest. On all sides we see evidences of alleged upheavals or 

 depressions of laud : we know, for instance, that Scandinavia, 

 Scotland, all of Northern Asia, Alaska, and Texas are now rising 

 out of the sea; we are told that the coasts of New Jersey, Long 

 Island, Cape Breton, and Greenland are now sinking beneath the 

 sea. Here were undeniable facts directly opposed to each other and 

 to my assumption that these movements must be universal in kind 

 over either hemisphere. 



These conflicting facts, which seemed to deny and refute these 

 other facts mentioned, as obtained from the raised beaches, and to- 

 the accumulation of which I have devoted so many years' labour, 

 seemed to assure me of failure from the first ; but notwithstanding 

 the discouraging outlook, search was undertaken for evidence of 

 these periodic vibrations in the oceanic surface, no hope being 

 entertained at that time, however, of finding explanation of those 

 discordant motions, existing in the same hemisphere, to which 

 attention has been called. My only hope was that these fluctuations 

 might be found periodic in their nature. 



