Ixxxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May I904. 



Further consideration of the subject has shown that, while 

 Playfair's conclusion may be accepted as a true explanation of local 

 changes of relative level, yet that alterations of sea-level, wide in 

 their geographical extent and serious in their vertical amount, may 

 be brought about by movements of the hydrosphere, and without 

 any movement, upward or downward, of the land. It is now 

 recognized, for example, that the attraction of masses of high laud 

 must seriously raise the level of the adjacent seas, and that a 

 similar effect will follow from the accumulation of a massive ice- 

 cap at either pole. There can be little doubt, also, that during the 

 secular cooling and contraction of the planet, the floor of the ocean- 

 basins is progressively sinking, and that the consequence of this 

 subsidence must be a proportionate emergence of land. But we 

 are profoundly ignorant of the rate at which such subsidence takes 

 place. Probably it is, on the whole, exceedingly slow, although it 

 ma3 T be varied by occasional collapses, which, when they take place, 

 doubtless give rise to gigantic seismic waves. 



The objections which liobert Chambers and others made to the 

 acceptance of Playfair's doctrine of the practical invariability of 

 the sea-level have been augmented by various writers in more 

 recent years, and most notably by my distinguished friend Prof. 

 Suess. After a detailed investigation of the evidence adduced in 

 favour of the elevation and subsidence of land, the great Austrian 

 geologist has come to the conclusion that this evidence has been 

 misinterpreted, that there are no vertical movements of the litho- 

 sphere (except such as may be connected with the secular contrac- 

 tion of the planet, as in the formation of mountain-chains), and that 

 the doctrine of the slow uprise and sinking of countries is a mere 

 phantasy, like the old ' Erhebungstheorie,' of which he regards it as 

 a relic. This view he has interwoven in the magnificent and im- 

 pressive picture which he has drawn of the grand march of the 

 evolution of the earth's surface-features. Let me not be thought 

 to be wanting in admiration of his great ; Antlitz der Erdc," if I 

 venture to express my dissent from this particular doctrine, which 

 is there expressed with all the fullness of knowledge and literary 

 skill of which its author is so consummate a master. 



Prof. Suess's opinions as to the secular elevation and depression 

 of land have not escaped opposition and criticism, especially 

 on the part of the geologists of those countries from which the 

 classic examples of terrestrial upheaval have been drawn. But 

 coming to us, as they do, from one gifted with such high powers 



