130 GEOLOGICAL CHANGE, AND TIME. 



memorial of mauy successive stages iu geographical evolutiou. Within 

 certain limits land and sea have changed places again and again. 

 Volcanoes liave broken out and have become extinct in many countries 

 long before the advent of man. Whole tribes of plants and animals 

 have meanwhile come and gone, and in leaving their remains behind them 

 as monuments at once of the slow development of organic types, and 

 of the prolonged vicissitudes of the terrestrial surface, have furnished 

 materials for a chronological arrangement of the earth's topographical 

 features. Nor is it only from the organisms of former epochs that 

 broad generalizations may be drawn regarding revolutions in geog- 

 raphy. The living plants and animals of to-day have been discovered 

 to be eloquent of ancient geographical features that have long since 

 vanished. In their distribution they tell us that climateshave changed ; 

 that islands have been disjoined from continents; that oceans once 

 nnited have been divided from each other, or once separate have now 

 been joined; that some tracts of land have disappeared, while others 

 for prolonged periods of time have remained in isolation. The pres- 

 ent and the past are thus linked together, not merely by dead matter, 

 but by the world of living things, into one vast system of continuous 

 progression. 



In this marvellous increase of knowledge regarding the transforma- 

 tions of the earth's surface, one of the most impressive features, to my 

 mind, is the power now given to us of perceiving the many striking 

 contrasts between the present and former aspects of topography and 

 scenery. We seem to be endowed with a new sense. What is seen by 

 the bodily eye — mountain, valley, or plain — serves but as a veil, beyond 

 which, as we raise it, visions of long-lost lands and seas rise before us 

 in a far-retreating vista. Pictures of the most diverse and opposite 

 character are beheld, as it were, through each other, their lineaments 

 subtly interwoven, and even their most vivid contrasts subdued into 

 one blended harmony. Like tlie poet, "we see, but not by sight alone;" 

 and the "ray of fancy" which, as a sunbeam, lightened up his land- 

 scape, is for us broadened and brightened by that play of the imagina- 

 tion which science can so vividly excite and prolong. 



xVdmirable illustrations of this modern interpretation of scenery are 

 sup])lied by the district wlierein we are now assembled. On every -side 

 of us rise the most convincing proofs of the reality and potency of that 

 ceaseless sculpture by which the elements of landscape have been carved 

 into their present shapes. Turn where we inay, our eyes rest on hills 

 that project above the lowland, not because they have been upheaved 

 into these positions, but because their stubborn materials have enabled 

 them better to withstand the degradation which has worn down the 

 softer strata into the plains around them. Inch by inch the surface of 

 the land has been lowered, and each hard rock successively laid bare has 

 communicated its own characteristics of form and color to the scenery. 



