34 THE PAST CONDITION 



exhilarated on being turned into a new field of inquiry, 

 and to go off at a hand-gallop, in total disregard of hedges 



1 ditches, losing sight of the real limitation of their 

 inquiries, and to forget the extreme imperfection of what 

 is really known. Geologists have imagined that they 

 could tell 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 little 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 



1 ory 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 prac- 

 ticable. 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 

 lower beds are all older than the upper 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 



"iitinuous, there is absolutely no means whatever 



n you by the nature of the deposit of saying whether one 



neh Younger or older than the other ; but you may say, 

 .< s::id and think, that the case is very much 



i <-d if fhr beds \\hich wo are comparing are continuous. 

 Suppose t\\.. >f mud hardened into rock, A and 



ion (Fig. 5). 



. vou s;t\. it is admitted that (lie lowermost bed 

 vs the Older. Very well ; H, therefore, is older 



M A. No doubt, as a whole, it is so ; or if any parts 



of the two beds which are in the same vertical line are 



1. it is so. Hut suppose you take what seems a 



natural slop further, and say that the part a of the 



