UNCLE IN ENGLAND. 221 



covered here and there by vegetation, yet you 

 can easily trace it as it slopes upwards, till you 

 see it actually arrive at the upper edge of the 

 cliff. It is the same with all the strata, which 

 lie either above or below it : you see they rise 

 successively towards the surface ; and if there 

 be numerous other strata under the valley, and 

 which therefore we cannot see, still they also 

 will reach the surface further off. The place 

 where any stratum makes its appearance on the 

 surface is called its out-crop; and as they range 

 themselves there in regular succession, you must 

 at once perceive that in examining the surface, 

 in a direction crossing the strata, you would find 

 as complete a section of them as you now see 

 in the face of the cliff, or as you could obtain by 

 boring perpendicularly through them." 



He said a great deal more on this subject, and 

 helped us to follow with our eyes several other 

 strata to their out-crop. " This circumstance," 

 he added, " is of immense importance to the 

 geologist; for if the strata were all horizontal, 

 we should be ignorant of everything below the 

 mere external crust of the earth. Sometimes, 

 indeed, a deep well, or the workings of a mine, 

 might reveal the nature of the interior for a few 

 hundreds of feet or yards ; whereas by examin- 

 ing the out-crop of the inclined strata, we can 

 ascertain not only their succession, but their 

 composition, for many miles in thickness. An- 



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