168 H. W.Pearson — Oscillations of Sea- level. 



N. S. Sbaler also says, that some of the apparent upheavals and 

 depressions of the land may be due to absolute changes in the sea-level 

 (" Geological Eecord," 1875, p. 178) ; and these men are supported 

 in their rejection of the old theory of Strabo, which had been adopted 

 by Playfair, Von Buch, and Lyell, by Edouard Suess, Dr. Schmick, 

 and Trautschold, the latter claiming that " many of the phenomena 

 of sedimentation and deposition attributed by geologists to a sub- 

 sidence of the crust are, in fact, due to periodic oscillations or 

 upheavals of the oceanic surface " {Science, vol. iii, p. 342). 



These citations demonstrate that the matter of the permanency 

 of the sea-level is to-day one of the unsettled questions of geology, 

 and I believe it to be more fundamental in its nature than any other 

 unsolved geological problem. It should be of interest, then, to learn 

 why these conflicting opinions between our great geologists have 

 existence. Why have the teachings of Playfair, Von Buch, and 

 Lyell, adopted^for three-fourths of a century, been in the last quarter 

 of a century questioned from every direction ? 



Investigation allows us to answer this question. The old beliefs, 

 in the absence of knowledge, were based on infei'ence. The latest 

 beliefs, rejecting inference, are based on observation, on an enormous 

 accumulation of facts, that were entirely unknown to Playfair and the 

 other disciples of Strabo, and these facts it is impossible to explain 

 through the older theory. 



For instance, Playfair's argument, on which the theory of an 

 invariable sea-level rests, is as follows : — " In order to depress or 

 elevate the absolute level of the sea by a given quantity, in any one 

 place, we must depress or elevate it by the same quantity over the 

 loTiole surface of the earth [my italics], whereas no such necessity- 

 exists with respect to the local elevation or depression of the land " 

 (" Principles," 9th ed., p. 523). 



Now the very foundation of this argument, a position unimpeach- 

 able in the time of Playfair and of Von Buch, is to-day absolutely- 

 untenable. The hypothesis of Adhemar, the knowledge that great 

 masses of ice at one time existed in the Northern Hemisphere, and 

 that submergence of the Northern, coexistent with emergence of 

 the Southern Hemisphere, must have been the necessary consequence, 

 as demonstrated mathematically by Dr. Croll, by Lord Kelvin, by 

 Archdeacon Pratt, by Fisher, Heath, Woodward, and many others, — 

 these arguments, I say, teach us that the contention of Playfair, Von 

 Buch, and Lyell, valid perhaps in its day, is no longer to be accepted, 

 and if the theory of a variable sea-level is to be rejected, reasons 

 more solidly grounded must be accorded us. 



It seems now impossible to reject the idea that upheaval of the 

 sea surface in the north, and subsidence in the south, may be going 

 on at one and the same time, and in addition to this the writer has 

 shown how a local upheaval of the oceanic surface in one hemisphere 

 may, nay must, be coexistent with a local depression of this surface 

 at some point in the same hemisphere, provided the slightest variation 

 of flow in the oceanic currents shall take place. (See The American 

 Geologist, Sept. 1899, p. 192.) 



