anniversary address of the president. xcl 



Conclusion. 



It only remains for me, in conclusion, to make one or two ob- 

 servations on a subject which, in the present condition of our science, 

 appears to me too important to be lost sight of, and which, if neg- 

 lected, may lead to many useless discussions and unfortunate mis- 

 conceptions. However paradoxical it may sound, I believe that, as 

 our knowled^-e of geological formations advances, some of our diffi- 

 culties increase. We have found during late years that, in proportion 

 as we extended our knowledge of different formations, we have been 

 compelled not only to introduce a greater number of principal forma- 

 tions, but to subdivide these again into groups, and again to sub- 

 divide the groups into distinct beds. This process has long con- 

 tinued. We are no longer satisfied with primary, secondary, and 

 tertiary epochs ; it is not enough that we have introduced the Per- 

 mian, the Neocomian, and similar terms to designate different periods, 

 or that we have subdivided the Secondary rocks into Triassic, Liassic, 

 Jurassic, and Cretaceous ; all these divisions are again subdivided, I 

 might almost say, " ad infinitum.^'' As the investigation of geologists 

 has extended itself over distant countries, and has brought fresh con- 

 tinents under our notice, new and at first sight anomalous combina- 

 tions have been brought to light. The limits and breaks already 

 assigned to different formations in the countries where first observed, 

 have not been found always to hold good. The marked unconforma- 

 bility of stratification and the distinct differences of paleeontological 

 evidence, on which the limits of formations were first grounded, have 

 in other countries either disappeared altogether, or have required to 

 be greatly modified. It has been found that between these respective 

 limits, as at first laid down, certain fossils of the lower beds extend 

 higher up into those above, while some of those hitherto supposed to 

 be characteristic of the overlying formation are found extending 

 downwards into beds of an older age. On the other hand, that 

 unconformability of strata which was supposed to mark the limits 

 of epochs, and to point out the breaks occasioned in the successive 

 deposition of strata by great natural convulsions, is often found to 

 disappear when the investigation is extended and the strata are traced 

 into other countries. In this dilemma the first step has been to 

 intercalate new beds as intermediate between the different formations, 

 connecting them as it were by a certain community of animal life, 

 marking the passage from one condition of existence to another ; as, 

 for instance, the S. Casciano beds are now introduced between the 

 Triassic and the Liassic, the Carboniferous shales between the Old 

 Red Sandstone and the true Carboniferous beds, and others which 

 will readily occur to you. But the difficulty does not cease here. 

 As we extend our inquiries, we find that the gradual passages from 

 one formation to another become more frequent, and that the breaks 

 in the conformability of strata, instead of being the normal condition 

 of the passage from one formation to another, are mere local phseno- 

 mena, and we are thus almost forced to the conclusion that such 

 marked separations between the different formations as we have been 



