Recent Sinking of Ocean-level. 247 



suggestion is published, not to express a fixed conclusion, but to 

 invite criticism by those familiar with shorelines in different parts 

 of the world, for the testing of the idea is manifestly a worldwide 

 problem. 



The matter is important because it affects judgment as to the 

 reality of many so-called uplifts of land or sea-bottom, and because 

 a close study of the latest shift of sea-level may help to systematize 

 the criteria for earlier and larger eustatic shifts. 



Field Observations. 



First Contact with the Problem. — The hypothesis of a Eecent, 

 negative shift of sea-level first suggested itself to the writer nearly 

 twenty years ago, while engaged in the correlation of post-Glacial 

 elevated strands in Labrador and Newfoundland with those of 

 Quebec. The highest strand mapped between Newfoundland and 

 Nachvak Bay, 500 miles to the north-west, was found to be strongly 

 warped ; its gradient varies from 1 to 3 feet per mile, measured 

 along the coast and thu^s not at right angles to the isobases. The 

 highest strand in Maine has maximum gradients of 5 or more 

 feet per mile. Ice attraction fails to account for such high values 

 and even for the lower gradients of the old strands around the Great 

 Lakes, where also crustal warping is generally credited. On the 

 other hand, the lowest emerged terrace along the shores of the Gulf 

 of St. Lawrence was seen to be conspicuously level throughout a 

 distance of 300 miles or more below Quebec City. The apparent 

 uniformity of level prompted the question whether this particular 

 strand had been abandoned by the waves because of a sinking of 

 general sea-level. For lack of accurate levelling, definite correlation 

 with the more closely studied, lowest beaches of Labrador was 

 impossible, and with the data in hand serious belief in the hypothesis 

 of a eustatic change was withheld. 



However, that explanation was recalled by the discovery of new 

 facts during recent field studies on the shores of New England, 

 Florida, and the Samoan Islands. Meantime, Goldthwait had made 

 a careful study of the St. Lawrence strand, to which he gave the 

 name " Micmac terrace " ; the results of his levelling agree so M^ell 

 with those made in the other regions mentioned that the suspicion 

 of past years has become a hypothesis that seems to deserve more 

 attentive consideration. 



For the opportunity to collect data from the two tropical regions 

 the writer is indebted to Dr. A. G. Mayor, Director of the Marine 

 Laboratory of the Carnegie Institution of Washington. 



Gulf of St. Lawrence. — In his excellent account of the Micmac 

 terrace, Goldthwait writes : " Traces of wave work along the south 

 coast of the Saint Lawrence were found at all altitudes below the 

 upper limit of submergence. Contrary to expectation, again, there 

 proved to be no shoreline below the highest one, with the exception 

 of the twenty-foot [Micmac] strand, which possesses enough 



