MATERIALS 25 



be retained. But if the foregoing gloomy, though not 

 unduly pessimistic, sentences should induce a few more 

 lovers of Nature to preserve any fossils they see, the 

 main purpose of this book will have been achieved. A 

 man who finds an ancient inscription or roll of papyrus, 

 lying in a place where destruction is inevitable, and 

 who leaves it to decay, is hardly less a vandal than one 

 who deliberately destroys it. The history of the Earth 

 and its inhabitants is a wider problem than that of 

 merely human progress. The documents are less com- 

 plete, and most of them must needs perish unread. 

 Those that can be saved must be rescued at the first 

 opportunity. With fossil-collecting it is always a case 

 of " now or never." 



Every fossil, then, should be an object of veneration. 

 However imperfect or obscure it may be, it is a repre- 

 sentative of hundreds, perhaps thousands, of organisms 

 whose remains were not preserved, or will never fall 

 into human hands. Let those hands deal gently and 

 reverently with such as have survived risks innumerable 

 to give their fragment of testimony on the history of 

 Life! 



(B) THE OCCURRENCE OF FOSSILS 



(I) FOSSILIFEROUS AND UNFOSSILIFEROUS ROCKS 



The three rock-types that make up the bulk of the 

 Earth's crust are described, from the modes of their 

 formation, as Igneous, Metamorphic and Sedimentary. 

 The first type is the product of consolidation of Magma, 

 a complex mineral solution that can be developed only 

 at considerable depths. When solidification takes place 

 underground, the rocks formed cannot be expected to 

 contain any traces of life. But when magma is extruded 

 as lava, it may occasionally catch up organic remains 



