GEOLOGICAL CHANGE, AND TIME. 131 



li\ standiiijj;- on the (Jiistle Hook, the central and ohlest site in Edin 

 burgh, we aHow the bodily eye to wander over the lair landscape, and 

 the mental vision to rau<it; through the long vista of earlier landscapes 

 which science here reveals to us, what a strange series of i)ictures passes 

 before our gaze ! The busy streets of to-day seem to fade away into the 

 mingled copsewood and forest of pre-historic time. Lakes that have long 

 since vanished gleam through the woodlands, and a rudecam)e pushing 

 from the shore startles the red deer that had come to drink. While we 

 look, the picture changes to a jxtlar scene, with bushes of stunted Arctic 

 willow and birch, among which herds of reindeer browse and the huge 

 mammoth makes his home. Thick sheets of snow are draped all over the 

 hills around, and far to the northwest the distant gleam of glaciers and 

 snowtields marks the line of the Highland mountains. As we muse (m 

 this strange contrast to the living world of to day the scene appears to 

 grow more Vrctic in aspect, until every hill is buried under one vast 

 sheet of ice, 2,(»0() feet or more in thickness, which fills up the whole 

 midland valley of Scotland and creeps slowly eastward into the basin of 

 the North Sea. TTere the cuitain drops ujton our moving pageant, for 

 in the geological record oi this })art of the country an enormous gap 

 occurs before the coming of the Ice Age. 



When once moie the sjtectacle r(\sumes its movement the scene is 

 found to ha\e utterly changed. The familiar hills and valleys of the 

 Lothians have disapi)eared. Dense jungles of a strange vegetation — 

 tall reeds, club mosses, and tree-ferns — spread over tlu^streamiug swam i»s 

 that stretch for leagues in all directions. Broad lagoons and oi)en seas 

 arc dotted with little voh'-anic cones which throw out their streams of 

 lava and showers of ashes. Beyond these, in dimmer outline and older in 

 date, we descry a wide lake or inland sea, covering the whole midland 

 valley and marked witli long lines of acti\e volcanoes, some of them sev- 

 eral thousand feet in height. And still furtlierand fainter over the same 

 region, we may catch a giimjjse of that si ill earlier exj)anseof sea which 

 in Siluiiaii times oversi)read most of Brifian. Butl)eyond this scene our 

 vision fails, VV^e have reaclunl the limit across which no geological 

 evidence exists to lead the imagination into the primeval darkness 

 be>()nd. 



Sucli in briefest outline is the succession of mental pictur«^s which 

 modern sci(Mice enables us to IVamcout of the landscapes around l^^diii- 

 bui-gh. TJH'y may be taken as illustiations of what may be drawn, and 

 sometimes with even greater fulness and vividnc^ss, from any district in 

 these islands. But 1 cite tiiem especially because of their local interest 

 in connection with the present meeting of the Association, and because 

 the rocks that yield them gave inspirati(»n to those great masters w hos(^ 

 claims on our recollection, not least for their e.\]>lanation of the origin 

 of scenery, I have tried to recount this e\ening. 



