CHAPTER I. 



INTRODUCTION. 



The economic value of fossils is commonly entirely 

 overlooked. To the laity usually these remains of life are 

 merely curious ; to the specialist the interest in the ancient 

 organisms is largely scientific. But with him who wills it, even 

 a slight acquaintance with the true character of fossils enables 

 the rocks to be read as a printed page. It is one of the best 

 established facts in modern geological science that there is an 

 intimate relation between mineral deposits and the surrounding 

 rocks ; hence the geological age of the particular beds becomes 

 an important factor in the early attempts to develop new min- 

 eral districts. This suggestion again rests upon one of the 

 cardinal principles of geology : that the geological succession 

 of strata is determinable readily by the remains of life con- 

 tained. Thus, in reality, fossils are labels on the rocks, telling 

 man at a glance the age of the bed he is working, and provid- 

 ing him with the most reliable guides he could possibly secure 

 to direct him to the layers most likely to contain the mineral 

 sought. As a good illustrative example, it is well understood 

 now that the coal of the Mississippi basin is confined to cer- 

 tain limited horizons, ordinarily known as the Ooal Measures. 

 In the limestones and shales overlying the Carboniferous strata, 

 there are associated always certain very easily recognizable 

 fossils that are characteristic of the formation, and are not to 

 be found elsewhere. A very little study of these forms soon 

 determines whether or not the rocks of any given district are 

 liable to furnish coal. Yet every year large sums of money are 

 wasted in both this and the neighboring states in the fruitless 

 search for coal and other minerals in places where there is no 

 possibility whatever of success. Everywhere throughout the 



