58 



STRATIFICATION. 



sisting of one substance only, but that there are 

 various kinds of substances, such as soil, sands, 

 gravels, clays, limestones, slates, granite, &c, min- 

 gled together, perhaps, in apparent confusion, but 

 still presenting appearances which often interest 

 even the most ignorant observer. How interesting is 

 it to find, on more extended examination, that these 

 apparently confused masses are arranged in a regu- 

 lar order of succession, and that a slight acquaint- 

 ance with geological facts and principles furnishes 

 a clew to unravel, as it were, the intricate web of a 

 world's formation ! What advantage, too, does the 

 geologist possess over those whose observation is 

 not guided by the principles of science. He alone 

 knows where we may expect to find valuable min- 

 erals, such as coal, iron, salt, gold, silver, lead, &c. ; 

 and millions of dollars might have been saved in 

 searching for these hidden treasures had those en 

 gaged in the pursuit been acquainted with the merest 

 elements of the science. 



Rocks have been divided into stratified and un* 

 stratified. Stratified rocks are those which are di- 

 vided into beds parallel to each other, or which, 

 though not parallel, are arranged in separate layers. 

 Various disturbing causes may have destroyed the 

 parallelism of these beds ; still the term is retained, 

 and the beds are called strata. Indeed, it is a very 

 rare thing for the layers to be perfectly parallel or 

 horizontal, as the disturbing forces have deranged 

 their position, and thrown some above, while others 

 remain depressed below the general level. 



Strata are said to be horizontal when they have 

 no inclination with the horizon, thus : 



Fig. 9. 



