400 Murchison’s Siluria. 
During my early researches, it was shown that the lowest of 
these (1833) fossil-bearing strata reposed, in the west of Shrop- 
shire, on a very thick accumulation of still older sediment, as ex- 
posed in the ridge of the Stiper Stones, and the Longmynd 
mountain; and the strata of the latter not offering a vestige of 
_ former life, they were consequently termed unfossiliferous grey- 
k 
supposed older sediments; for in obtaining all the knowledge I 
had then acquired, by receding from upper strata whose contents 
were known to lower and previously unknown rocks, I had invarl- 
ably found that the latter were characterized by many distinct and 
new organisms. This fact, which had been first established in 
the tertiary and secondary deposits, was thus proved to be univer- 
sally applicable by the occurrence of similar distinctions in the 
Carboniferous, Old Red, and Silurian rocks. 
t was, howéver, in vain that we looked to the production of a 
peculiar type of life from the “Cambrian” rocks. Silurian fos- 
sils were alone found in them; and the reason has since become 
manifest. The labors of many competent observers in the last 
fifteen years have proved that these rocks are not inferior in posl- 
tion, as they were supposed to be, to the lowest stratified rocks of 
my Silurian region of Shropshire and the adjacent parts of Mont 
gomeryshire, but are merely extensions of the same strata ; and 
hence the looked-for geological and zoological distinctions could 
never have been realized. In the following chapters it W! | be 
shown how Sir H. De la Beche, Professors Ramsay and EB. 
Forbes, with Mr. Salter, and other geologists and palzeontologists 
have demonstrated, that the fossil-bearing rocks of orth ¥ ales 
are both in their order and contents the absolute equivalents of 

