CI I. XXVI. WILLIAM SMITH. 



223 



on now, and that the only way to read the histoiy of the 

 past is to compare it with the present. 



William Smith surveys the Rocks of England. — Mean- 

 while another man, whom we must not forget to mention, was 

 working away very quietly without any help, and with very 

 little money ; and yet in his way was doing at least as much 

 work as the others. This was William Smith, a plain Eng- 

 lish surveyor, who was so much struck with the arrange- 

 ment of the different formations in the hills among which 

 he travelled that he determined to try and map them out 

 so as to show exactly how the strata are placed one above 

 the other, and what counties they pass through. 



He began his work in 1790, and travelled over the whole 

 country, chiefly on foot, marking as he went all the different 

 positions of the rocks, and collecting the shells and other 

 fossils which he found in them. He had not gone on long 

 before he observed that certain fossils which appeared in the 

 lower beds disappeared when he reached those which lay 

 above them, and that others took their place j so that in this 

 way it was possible to use the fossils to trace out the age of 

 any particular rock, just as the face of a coin helps you to 

 tell the reign in which it was cast ; and the story told by 

 the fossils agreed very well with the divisions which he had 

 worked out by the position of the rocks above each other. 

 He was even so observant tliat he distinguished between 

 the fossils which had their edges fresh, showing that they 

 had not been disturbed since they were buried in the earth, 

 and those which were rubbed and water-worn. The fresh 

 ones only, he said, are of use to tell the age of a rock, for 

 those which are rubbed may have been washed out of some 

 older formation by rivers. 



In this way William Smith, for pure love of science, and 



