VI 



Murchison 255 



by the banks of the Wye, he published his great work, 

 The Silurian System, a massive quarto of 800 pages, with 

 an atlas of plates of fossils and sections, and a large 

 coloured geological map. 



The publication of this splendid monograph forms a 

 notable epoch in the history of modern geology, and well 

 entitles its author to be enrolled among the founders of 

 the science. For the first time, the succession of fossili- 

 ferous formations below the Old Eed Sandstone was 

 shown in detail. Their fossils were enumerated, described 

 and figured. It was now possible to carry the vision 

 across a vast series of ages, of which hitherto no definite 

 knowledge existed, to mark the succession of their 

 organisms, and thus to trace backward, far farther than 

 had ever before been possible, the history of organized 

 existence on this globe. 



While carefully working out the stratigraphy of the 

 rocks, Murchison had come upon various masses of erup- 

 tive rock. Some of these he recognized as intrusive, others 

 he saw to be lavas and ashes which had been ejected over 

 the floor of the ancient ocean. In this way he was able to 

 present a picture of extraordinary interest, in which the 

 geologist could mark the position of the old seas, trace the 

 distribution of their organisms, and note the sites of their 

 volcanoes. 



Even before the advent of his volume, his remarkable 

 results had become widely known, and had incited other 

 observers all over the world to attack the forbidding 

 domain of Greywacke. In France, his classification had 

 been adopted, and applied to the elucidation of the older 

 fossiliferous rocks by Elie de Beaumont and Dufrenoy, who 



