INTRODUCTION. 



7 



rocks having distinctly that mineral character, both above and below those which I 

 describe. 



A geographical term was finally adopted, derived from the Silures, whose power 

 extended over the region where these rocks are best displayed, and the name of whose 

 illustrious chief, Caradoc (Caractacus) , has been transmitted to us in a bold range 

 of hills, composed of one of the most important formations of the system to be de- 

 scribed. The term was no~ sooner proposed than sanctioned by geologists, both at 

 home and abroad, as involving no theory, and as simply expressing the fact, that in 

 the " Silurian region," a complete succession of fossiliferous strata is interpolated betiveen 

 the Old Red Sandstone and the oldest slaty rocks. 



M. Elie de Beaumont, for example, warmly encouraged me to use this name, and 

 with his coadjutor M. Dufrenoy has since materially contributed to give it currency on 

 the Continent. Soon afterwards M. Boue and M. de Verneuil announced the diffusion 

 of " Silurian" rocks in Servia and the adjacent parts of Turkey in Europe, while our 

 countrymen Hamilton and Strickland extended their range to the Thracian Bosphorus. 

 More recently, M. Forchhammer of Copenhagen has visited the " Silurian region" to 

 endeavour to recognize in it the rocks of Scandinavia ; and even whilst I write, MM. D' 

 Omalius D'Halloy and Dumont are exploring it to establish a parallel between its de- 

 posits and those of Belgium. Lastly, I may state, that M. de Boblaye has honoured 

 me by offering to translate this work into the French language. 



Shortly after I proposed the name " Silurian," one or two European tracts were, 

 indeed, pointed out as resembling that which I had selected as a type. One of the 

 most remarkable is on the southern frontier of the Ardennes, where three forma- 

 tions were recognised by Dr. Buckland and Mr. Greenough as occupying the same geo- 

 logical position as in England and Wales j namely, between the carboniferous deposits 

 and the older slaty rocks. 



That similar deposits exist in many parts of Europe is evident from the works of 

 Strangways, Brongniart, Von Buch, Hisinger, Dalman, Keilhau, and other writers, as 

 well as from the fossils found in Norway, Sweden, Russia, Poland, Germany and France ; 

 though patient comparisons must be instituted before the peculiar relations of the Si- 

 lurian Rocks of those countries can be established 1 . 



Their spread through distant regions will be again brought under consideration, in the 

 concluding view of the general distribution of organic remains. In the mean time it 



1 I cannot attempt to enumerate the names of all the foreign authors who have written on Transition Rocks, 

 though many of those who treat of the Organic Remains are alluded to hereafter. See Part II. Judging from 

 the maps of Hisinger and Keilhau, I presume that both Upper and Lower Silurian Rocks exist in several di- 

 stricts of Sweden and Norway. It would appear that I may have been led into an error (p. 169 note) in sup- 

 posing that the Old Red Sandstone occurs in these regions. I hope, however, at some future day, to examine 

 personally the older rocks of Scandinavia and Russia, and to show to what extent they agree with those of our 

 own country. 



