GEOLOGY. 305 



menced since the publication of Sir Roderick's first great work, to tinder- 

 stand now the peculiar condition of palaeozoic geology at the time he 

 started upon his scientific mission. All seems so orderly, clear, and self- 

 evident Silurian, Devonian, Carboniferous, and Permian, being words 

 that convey definite and precise meanings to the youngest student of a 

 school of mines or geological class-room that we cannot picture to our- 

 selves the darkness and confusion out of which the definitions were elimi- 

 nated. 



It is the proud boast of British geologists that the foundations of many 

 of the great sections of their science, and the establishment of most of the 

 realms in time enrolled in the scale of formations constituting the crust of 

 the earth, were originated within their native archipelago. The very pro- 

 vincial jargon of working miners and quarrymen, and the local appella- 

 tions given to rock and soil by our peasants, have become scientific terms, 

 established in the language of philosophical treatises all over the world. 

 When a name was wanting, and could not be taken from these illiterate 

 sources, it was struck in a British mint ; and among all the stamps that 

 mark the world's rocks as British claims, one of the most widely current 

 and permanently graven is that of " Silurian." An old British people, a 

 tribe of borderers, who, under the leadership of the famous Caractacus, 

 fought the llomans, has given its name to far- spreading territories ; and 

 could the old Silures be summoned once more to life, they would have 

 some difficulty in finding the true Siluria, so many offsets of their ancient 

 kingdom are now dotted over the map of the world. Since the system 

 named after this province was first announced, Silurian strata have been 

 detected far and wide over the face of the earth. In Germany, France, 

 Scandinavia, Russia, Spain, and the Mediterranean, a Silurian basis has 

 been found on which the other fossiliferous rocks successively repose. In 

 Siberia, China, and India, Silurian strata have either been already demon- 

 strated, or the next thing to it. In both North and South Africa the rocks 

 that come next in order have already been detected. In Australia well- 

 marked Silurian types are proved to exist. In North America is one of 

 the grandest developments of the Silurian system in the world, that dis- 

 plays both physical and palaDontological features in wonderful variety and 

 profusion. In South America there are indications of strata of similar age. 



From a recent work of Sir R. Murchison, we make the following ex- 

 tract relative to the vertical dimensions of the Silurian rocks of the British 

 Isles, which will in a measure serve to show the lion -geological reader the 

 immensity of the formations under discussion, and the vast lapses of time 

 that must have rolled on during their deposition : 



" We have as yet no means of accurately estimating the thickness of 

 the older deposits of Scotland and Ireland ; but I find, on consulting with 

 Professor Nicol, that the Scottish section given can hardly represent less 

 than 50,000 feet; although we have no indication that the bottom of the 

 sedimentary series is reached, nor have we any tiling like a completion of 

 the Upper Silurian rocks. 



