285 



The collection, arrangement, examination, and description of 

 minerals, rocks, and fossils is, however, only a small part of the 

 scope of geological science. A man might be able to recognise 

 their species and varieties and to describe any new kinds he should 

 meet with ; he might be a good mineralogist, or an able petro- 

 grapher, or an excellent authority on the structure of fossil plants 

 and animals, and yet not be in the wider sense a geologist. It is 

 not enough to know the minerals, rocks, and fossils in liand speci- 

 mens such as can be displayed and examined in museums. The 

 yoiqgbt requires to study, them as they occur in nature. He 

 finds that in the solid mass of the globe the materials are not 

 thrown together wholly at random, but that certain broad general 

 laws have regulated the accumulation of these materials. He ascer- 

 tains that the rocks which have been deposited in water lie more 

 or less regularly arranged in parallel beds or layers, and constitute 

 by far the largest part of the solid crust of the earth accessible to 

 observation. He sees that these water-formed strata, as indicated 

 by the remains of plants and animals with which they are abun- 

 dantly charged, were in some cases formed on land or in fresh 

 water, but in most cases in the sea. Recognising marine shells in 

 rocks now elevated to heights of many thousands of feet above the 

 sea-level, he obtains proof of great upheavals of the earth's surface, 

 and can show that over the sites of even the loftiest mountains the 

 sea has rolled. , He further discovers that the oldest rocks of a 

 country have in many cases been upturned before the next serin 

 was laid down'upon them ; that these, again, were disturbed before 

 the deposition of the succeeding aeries, and thus be can demon- 

 strate that many mountain chains have not been the result of a 

 single movement, but of a long succession of more or less exten- 

 sive crumplings carried on at wide intervals during a protracted 

 series dfgmJnjlfiri period*. By the aid of his fossil evidence be 

 can fix the relative dates of these successive upheavals, and can 

 OMBfUfg the geological age of one mountain range with that of 

 another. He traces, moreover, the existence of numerous frac* 



