xM 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



place, and a rude estimate might be made of the number of cubic 

 feet of lava and scorise poured or cast out of various craters. The 

 amount of mud and sand deposited in deltas, and the advance of new 

 land upon the sea, or the annual retreat of wasting sea-chffs, are 

 changes the minimum amount of which might be roughly estimated. 

 The quantity of land raised above or depressed below the level of the 

 sea might also be computed, and the change arising from such move- 

 ments in a century might be conjectured. Suppose the average rise 

 of the laud in some parts of Scandinavia be five feet in a hundi'ed 

 years, the present sea-coast might be uphfted 700 feet ui fomteen 

 thousand years ; but we should have no reason to anticipate, from 

 any zoological data hitherto acquired, that the molluscous fauna of 

 the nonhem seas would in that lapse of years undergo any sensible 

 amomit of variation. If a botanist were asked how many earth- 

 quakes and volcanic eruptions might be expected, and how much the 

 relative level of land and sea might be altered, or how far the prin- 

 cipal deltas will encroach upon the ocean, or sea-chffs recede from 

 the present shores, before the species of European forest-trees die out, 

 he would reply that such alterations in the inanimate world might be 

 multipHed mdefinitely before he should have reason to anticipate, by 

 reference to any known data, that the existing species of trees in our 

 forests would disappear and give place to others. In a word, the 

 movement of the inorganic world is obvious and palpable, and might 

 be likened to the minute-hand of a clock, the progress of which can 

 be seen and heard, whereas the fluctuations of the living creation are 

 nearly invisible, and resemble the motion of the hour-hand of a time- 

 piece. It is only by watching it attentively for some time, and com- 

 paring its relative position after an interval, that we can prove the 

 reahty of its motion. If therefore in the coal-measures of South 

 Wales or Nova Scotia we find the same fossil trees repeated through 

 a mass of strata foimed in shallow water 10,000 feet thick, we ought 

 not to feel surprised, but merely conclude that foiTnerly, as now, the 

 rate of change in the vegetable kingdom was extremely slow, so that 

 a stupendous mass of stratified sand and mud, as well as great revo- 

 lutions in physical geography, might be slowly effected, without there 

 being time for any important fluctuation to be brought about in the 

 species of plants inhabiting the globe. 



I have endeavoured to show in mv ' Second Visit to the United 



