CLASSIFICATION OF THE SILURIAN ROCKS. 21 
Charles Lyell, in his ‘Travels in North America,’ and in other earlier works, adopted the 
same classification. 
In Germany, indeed, the system was also successfully developed in the same sense by 
M. Barrande, in his classical work the ‘ Bassin Silurien de Bohéme ;’ and in British North 
America it has since been most thoroughly worked out on exactly the same basis, 
both as to its fossil contents, and its relations to inferior and superior rocks, by that sound 
geologist Sir William Logan. 
Desirous of showing the generalisation to which the Silurian System had thus been 
extended to various countries, including its range over Russia and Scandinavia, as demon- 
strated by de Verneuil, von Keyserling, and myself,’ I next published the first edition 
of the work called ‘ Siluria,’ wherein I not only indicated the main features of the 
Silurian rocks in various countries, but also greatly augmented the figures and lists of 
characteristic fossils, many of which were ably described by Mr. Salter. In that work the 
relations of all the Paleozoic Rocks to each other, whether in Britain, or in the various 
foreign countries which had been sufficiently explored, were correlated and compared, 
including the Uppermost Palzeozoic deposits, to which, during my journeys in Russia, I 
had, with the approbation of my coadjutors, assigned the name of ‘ Permian.” 
As years rolled on, and as new discoveries were made, it became necessary to issue a 
new edition of ‘Siluria’ (1859). This volume was much enriched by descriptions of 
many additional fossils by Mr. Salter, by more defined sub-divisions of the various Silurian 
formations, resulting from the labours of the Geologists of the Government Survey, par- 
ticularly Mr. Aveline, by which the formation termed the Llandovery Rocks was inter- 
polated as a sort of middle group between the Caradoc Formation below and the Wenlock 
Strata above. This book was also specially marked by containing the result of my own 
researches in the North-west of Scotland, wherein I established, for the first time in the 
British Isles, the existence of stratified rocks of higher antiquity than any to which the 
names of Cambrian and Lower Silurian had been applied, for they were seen to underlie all 
such deposits, including limestones, with very ancient Lower Silurian types. These rocks 
I at first termed ‘“‘ Fundamental Gneiss,” and their position was illustrated in the coloured 
diagrammatic frontispiece of the work ; but, on being satisfied, from their order of infra- 
position to all the Palzeozoic Rocks then known, that they were the precise equivalents of 
the Laurentian System of British North America (so named by Logan), I, of course, adopted 
the name given to them by my eminent cotemporary. At that time, nothing organic had 
been discovered in the Laurentian Rocks of North America ; and the only fossil as yet dis- 
covered in the rocks to which the term Cambrian had been restricted was the Oldhamia, 
an organism of doubtful affinity, which has been placed respectively with the Polyzoa, 
the Hydroid Zoophytes, and even with the Calcareous Corallines and other Algze, The two 
1 See ‘ Russia and the Ural Mountains,’ 2 vols. 4to, Murray, 1845, with maps, numerous sections, and 
piates of fossils. 
