OF ORGANIC NATURE. 39 



us what was going on at all parts of the earth's surface 

 during a given epoch ; they have talked of this deposit 

 being contemporaneous with that deposit, until, from 

 our jfittle local histories of the changes at limited spots 

 of the earth's surface, they have constructed a universal 

 history of the globe as full of wonders and portents as 

 any other story of antiquity. 



But what does this attempt to construct a universal 

 history of the globe imply ? It implies that we shall 

 not only have a precise knowledge of the events which 

 have occurred at any particular point, but that we shall 

 be able to say what events, at any one spot, took place 

 at the same time with those at other spots. 



Let us see how far that is in the nature of things 

 practicable. Suppose that here I make a section of 

 the Lake of Killarney, and here the section of another 

 lake — that of Loch Lomond in Scotland for instance. 

 The rivers that flow into them are constantly carrying 

 down deposits of mud, and beds, or strata, are being as 

 constantly formed, one above the other, at the bottom 

 of those lakes. Now, there is not a shadow of doubt 

 that in these two lakes the upper beds are all older than 

 the lower — there is no doubt about that ; but what does 

 this tell us about the age of any given bed in Loch 

 Lomond, as compared with that of any given bed in 

 the Lake of Killarney? It is, indeed, obvious that if 

 any two sets of deposits are separated and discontinu- 

 ous, there is absolutely no means whatever given you 

 by the nature of the deposit of saying whether one is 

 much younger or older than the other ; but you may 

 say, as many have said and think, that the case is very 

 much altered if the beds which we are comparing are 



