Reports and Proceedings — Geological Society of London. 185 



all the invaluable discoveries that have been made in his science 

 with the microscope, merely because the objects are minute ? What 

 would become of astronomy, if everything was stripped from it that 

 could not be deduced by rough calculation from observations made 

 without telescopes ? With such striking examples before us, shall 

 we physical geologists maintain that only rough and imperfect 

 methods of research are applicable to our own science ? Against 

 such an opinion I certainly must protest ; and I argue that there is 

 no necessary connexion between the size of an object and the value 

 of a fact ; and that, though the objects I have described are minute, 

 the conclusions to be derived from the facts are great." 



i2,e:pok,17S j^isriD :pI^ocE:E]X)I^^C3-s. 



GrEOLOGiOAL SociETT OF LoNDON. — February 21st, 1872, — Prof. 

 Eamsay, F.E.S., Vice-President, in the Chair. — The following com- 

 munication was read : — "■ Migrations of the Graptolites." By H. 

 Alleyne Nicholson, M.D., F.E.S.E., F.G.S., Professor of Natural 

 History and Botany in University College, Toronto. 



The author commenced by stating that the occurrence of the same 

 species of marine animals in deposits in distant areas is now generally 

 regarded as evidence that such deposits are not strictly contempo- 

 raneous, but rather that a migration from one area to another has 

 taken place ; this migration he thought would probably in many 

 cases be accompanied by modification. Applying these principles 

 to the Graptolites, he endeavoured to show in what directions their 

 migrations may have taken place. 



He excluded from the family Graptolitidee the genera Dictyonema, 

 Dendrograpsus, Callograpsus, and Ptilograpsm, and stated that the 

 family, as thus limited, extended from Upper Cambrian to Upper 

 Silurian times. The earliest known Graptolites were those of the 

 Skiddaw Slates, which he thought would prove to belong to the 

 Upper Cambrian series. The Skiddaw area he considered to extend 

 into Canada, where the Quebec group belongs to it. Genera of 

 GraptoKtes belonging to this area are represented in Australia, and 

 this the author regarded as indicative of migration, but in which 

 direction was uncertain. Having discussed the forms of Graptolites 

 characteristic of the deposits in the Skiddaw-Quebec area, the author 

 proceeded to indicate the mode in which the family is represented 

 in the areas of deposition of the great Silurian series, namely, the 

 Llandeilo areas of Wales and Scotland, the Coniston area of the 

 North of England, the Gala area of South Scotland, the Hudson- 

 Eiver area of North America, and the Saxon and Bohemian areas, 

 giving under each of these heads a list of species, with indications of 

 their probable derivation. 



Discussion. — Mr. Etheridge commented on the importance of Dr. Nicholson's 

 paper, and on the difBculties attending the study of the Graptolitidaj. The migra- 

 tion of these organisms appeared to him to be very difficult to establish, especially in 

 connexion with their extension both eastwards and westwards. 



Mr. Hughes believed that if we could discover the original of any species, we 



