ORIGIN OF STRATIGRAPHICAL GEOLOGY. 59 



The second law is that every stratum may be 

 identified by means of the included remains of 

 plants and animals, termed fossils, which lived 

 when its rock material was being accumulated in 

 the part of the earth in which it is found. By 

 these fossils the exposed edge of every stratum 

 may be traced as it extends through the country. 

 Therefore the area occupied upon the surface of 

 the country by each geological deposit may be 

 drawn upon a map. A map made m this way, 

 which defines the limits of >trata, lava tlows, 

 crystalline and other rocks which form the coun- 

 try, is a Geological map. It shows how the strata 

 in a country may be distinguished and classified 

 by tlie - roups Of animals ami plants 



which have followed each other in occupying the 

 same portion of the Earth's surfai e. 



These laws were discovered about 1790 by 

 William Smith. He applied them in travelling 



through the countr] s to make the first Geo- 



logical Map of England and Wales, which was 



ipleted m 1815, In 1816 his collection of 



Slls, which distinguish and identify the several 

 British Strata, was placed in the British Museum. 

 It became the foundation of the National Geo- 

 logical Collection and the beginning of all Geo- 

 logical Museums. 



Other observers had recorded the order of the 

 strata in different localities, and in some cases 

 had recorded the occurrence of fossils in a single 

 stratum; but without making the discovery that 

 the strata may be identified by their organic re- 

 mains. 



Dr. Lister, in 1684, proposed to the Royal 

 Society to make a map of the soils in our coun- 

 try. This was the first proposal to make a Geo- 



