314 Britain's Heritage of Science 



were named from the localities where they were first or best 

 revealed to the hammer of the geologist, and so the lists of 

 the earliest fossiliferous rocks and their fossils are filled with 

 names dear to the tourist and the artist. 



The correlation of these by means of their fossils with 

 the rocks exposed in other areas rapidly followed, as, for 

 instance, by David Homfray, at Portmadoc, and soon the 

 unexpected Paradoxides and its associates were recognized 

 among the lowest beds of the fossiliferous rocks all the 

 world over. 



Other systems were determined in course of time : the 

 home of T. T. Lewis (1801-1858), of Aymestry, is still marked 

 by the Aymestry Limestone, while the position of the Llan- 

 dovery Rocks as now defined by the Survey was determined 

 by Dr. Williams, of Llandovery. The Llandovery Rocks were 

 subsequently cut off from the Caradoc Sandstone, and their 

 true position correctly fixed by Sedgwick under the name 

 May Hill Sandstone. A region so full of promise as the 

 borderland of Wales attracted Sir Roderick Murchison (1792- 

 1871), who, in the first half of last century, collated the 

 evidence and gave to the world in 1893, in his magnificent 

 work, the Silurian System beautifully illustrated by Sowerby. 

 The name Silurian is derived from the Silures of South Wales, 

 the ancient tribe which so long withstood the invading 

 Romans. 



In the meantime Prof. Adam Sedgwick (1785-1873), 

 stimulated by the work of Jonathan Otley in Cambria, and 

 with a personal acquaintance from childhood with the rocks 

 of the North of England, was attracted by the charms of a 

 wild and almost unexplored country, and threw all his energy 

 into the work of unravelling the succession of stratified rocks 

 exposed in the mountains of Cambria. His results were given to 

 the world in papers published by the Geological Society during 

 the same period and in other works in which the fossils were 

 figured and described by Salter and McCoy. It is to Sedgwick 

 that Geology owes the name Cambrian for the oldest known 

 group of fossiliferous rocks; and it was his genius which 

 introduced order into our knowledge of the older Palaeozoic 

 rocks of the North of England and W 7 ales, and laid the founda- 

 tions for subsequent work in the complicated regions where 



