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LNTRODUCTION. 
OBSERVATIONS 
ON THE 
CLASSIFICATION OF THE SILURIAN ROCKS; 
BEING 
AN INTRODUCTION TO THE DESCRIPTION OF THH BRACHIOPODA OF THAT SYSTEM, 
BY T. DAVIDSON, ESQ., F.R.S. 
BY 
SIR RODERICK I. MURCHISON, Barr., K.C.B., D.C.L., F.RS., 
DIRECTOR-GENERAL OF THE GEOLOGICAL SURVEY OF THE UNITED KINGDOM. 
Tuirty-onE years ago I proposed to geologists that the term “‘ Silurian” should be 
applied to a very extensive group of the lower sedimentary rocks which rise from beneath 
all those deposits the order and contents of which had then been systematically described. 
Having led the way in classifying these old deposits, by showing their true order of suc- 
cession, and the fossil remains of each subordinate formation, I have lived to enjoy 
the satisfaction of seeing the name ‘ Silurian” adopted in all parts of the world to 
which Geological Science has been extended. But, just as the proverb is true, “that 
Rome was not built in a day,” so the Silurian Classification, of which I launched the first 
outline in 1835, was but the prototype of that system into which it had to be developed 
by much labour in the field and closet. In 1838, I had, indeed, completed my main 
work upon the subject, with maps, sections, and a description of all the organic remains 
then known, under the title of ‘The Silurian System,’ founded on researches in eleven 
counties of England and Wales, or what I called the “Silurian Region,” because the 
famous Caractacus or Caradoc had been the British king of the tracts, occupied by the 
Silures, wherein the clearest evidences of the order of the strata were exhibited.' But 
' In the description of the fossils I was chiefly indebted to Mr. James de C. Sowerby and Mr. William 
Lonsdale; and I should fail to do justice to my own feelings, and to the reputation of a first-rate 
geologist, if I did not state, that, in the composition of the work, I was greatly aided by the last 
mentioned of these valued friends. In the later work ‘Siluria,’ the able paleeontologist Mr. J. W. Salter 
was my main assistant. 
