Vol. 60.] ANNIVERSARY ADDRESS. lxxxi 



attention, I have been unwilling that this time-honoured usage 

 should be wholly omitted from our programme to-day. Ro one 

 can more keenly regret than I do the enforced absence of our 

 President, and the consequent loss of the brilliant and suggestive 

 essay with which, had his health permitted, he would doubtless 

 have favoured us. I will not pretend to undertake to rill the gap 

 thus occasioned. All that I can attempt is to ask your attention 

 for a little to an old and familiar problem which has, during recent 

 years, once more come prominently forward in the copious litera- 

 ture of our science. I refer to the question of Changes in the 

 relative Levels of Sea and Land, and I propose to offer a 

 short summary of the present condition of the evidence which the 

 British Islands afford for the discussion of this subject. 



You are well aware that, among the later events in the geological 

 history of Western Europe, few have attracted more notice or have 

 given rise to more prolonged discussion than those which imply 

 changes in the relative positions of sea and land. Without entering 

 into the history of the controversy which began on this subject in 

 the middle of the eighteenth century, I may remind you that 

 Celsius in 1743 maintained that the proofs of apparent rise of land 

 in Sweden were to be explained by a measurable sinking of the 

 surface of the sea. This view was supported by Linnaeus, but did 

 not meet with universal acceptance, some observers holding that it- 

 was the land which was rising. An important contribution to the 

 discussion was made in 1802 by Piayfair, in his immortal 'Illus- 

 trations of the Huttonian Theory.' He conceived that 



• 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 

 whole surface of the earth.' (Op. cit. §392, p. 446.) 



He held that, although there is reason to believe that changes in the 

 solid ocean-floor do take place, which may affect the level of the 

 surface of the water, yet that such changes probably are compara- 

 tively slow and imperceptible. He concluded, therefore, that 



* the simplest hypothesis for explaining those changes of level, is, that they pro- 

 ceed from the motion, upwards or downwards, of the land itself, and not from 

 that of the sea.' (Op. cit. § 393, p. 447.) 



This deduction was generally accepted by geologists during the 

 greater part of last century, although it was disputed by a few 

 writers who maintained that, from various causes, the level of the 

 sea must be subject to considerable change. 



