PRESIDENTIAL ADDRESS. 6 



As aids to the correlation of the geological formations, fossils 

 began early to be used. At first they were treated merely as 

 tokens of the formations in which they occurred, without any 

 reference to their character as representatives of formerly exist- 

 ing life ; but it was soon perceived that by their use a system- 

 atic classification of the stratified rocks could be made. We 

 now know that without their use we could not have obtained 

 any adequate conception of geological history ; and the present 

 recognized scheme of the formations, or the geological scale, 

 as it is sometimes called, could have never been devised. It 

 is true that the order of succession of the few formations which 

 may be favorably exposed in limited districts might have been 

 made out by means of the lithological character of the strata 

 alone ; but the correlation of such limited groups of strata with 

 those of other and distant districts would have been by such 

 means impossible. 



After the order of succession of the different groups of strata 

 had been made out for certain regions and correlated with those 

 of other regions, it began to appear that certain types of animal 

 and vegetable remains characterized certain portions of the geo- 

 logical scale which was devised as a result of that correlation. 

 That scale, which is the foundation of the one now in general 

 use, was necessarily at first more or less defective and artificial. 

 It has from time to time been much improved, and, although it 

 is still imperfect, it is a marvellous monument of the results of 

 inductive reasoning. Geology and biology have each come to 

 the other's aid until not only has the foundation been substan- 

 tially laid, but the structure itself is approaching completion in a 

 perfect form. 



In Europe, where geological science was first studied, and 

 where it has ever since been prosecuted with remarkable energy, 

 it was found that the chronological range of the types of fossils 

 which characterize' the respective formations is well defined. 

 And when researches were extended into the adjacent parts of 



