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



The cause of this vibration in the oceanic waters it is perhaps 

 too early to discuss ; the oscillations should be first established 

 beyond a doubt. The most plausible explanation of the last change, 

 however, would seem to rest in a possible continued increase in 

 growth of the South Polar glaciers during the last few centuries, 

 contemporaneous with that general decrease in nearly all Northern 

 glaciers which, during the period mentioned, we know has been 

 in progress. If we could invoke this cause, the recent oscillation 

 mentioned would then be a physical necessity. 



The question raised in this paper, and the results that have been 

 reached, seem to warrant certain inferences or speculations, some of 

 which are liable to be of considerable importance. For instance, 

 we know that the landing-place of Columbus in 1492 has not yet 

 been positively identified ; our curve, however, calls for a sea-level 

 at that latitude and date some 12 to 15 feet higher than at present. 

 The question is, would the change in topography produced by 

 assuming the sea at its old position aid us in reaching final con- 

 clusion in this matter. 



As our curve for time past indicates a series of regular cycles 

 with a period of about 640 years, must we not suppose our oceanic 

 surface will again rise in the north, reaching its maximum shortly 

 after the j^ear 2100. If we prolong this curve, as suggested, we 

 must conclude that disaster, as repeatedly in the past, will soon 

 again overwhelm our northern coastlines. Are such cities as London, 

 Liverpool, and New York ready for this advancing sea, and has 

 such a region as Holland any too much time for preparation ? 



If our curve has been correctly mapped out, we must suppose that 

 the northerly movement of the waters has already commenced, or 

 that it will very shortly appear. This movement should be first 

 shown in cessation of the so-called upheaval of Scandinavia, and 

 that region should soon appear to be undergoing subsidence, while, 

 at the same time, the coasts of New Jersey will enter an epoch of 

 upheaval. We might, with great propriety, be on the look out for 

 these changes. 



Lord Kelvin has shown us how one inch of water taken from the 

 surface of the sea, and piled up as ice at the Pole, would appreciably 

 affect the rotation of the earth ; we can reasonablj'^ expect, therefore, 

 that these oscillations to and fro from the Poles to the Equator 

 of 15 or 20 feet, as our arguments and facts seem to require, 

 should have considerable efl"ect in altering the length of our day. 

 In fact, in this discussion we may, and probably will, find 

 confirmation of Newcomb's surmise, that the hitherto unexplainable 

 irregularities in the moon's motions may be due to slight changes in 

 the earth's axial rotation, which rotation perhaps •' varies from time 

 to time in an irregular manner" (" Popular Astronomy," p. 101). 



We thus see that there are reasons, many and weighty, inducing us 

 to pursue this investigation to greater extent. Notwithstanding the 

 considerable attention given to the subject by this writer, a research 

 involving the labour of many years, we are as yet merelj' on the 

 threshold of the inquiry. Years could be devoted to the comparison 



