150 Tlie Arnerican Geologist. ' September, isPs 
sors. It deals with the history of organisms, and therefore is 
able to find in fossils themselves the evidence of the order of 
sequence of the rocks containing them. 
I quoted from Bakewell, because he considered Deshayes' and 
Lyell's methods as innovations. When, in 1833, he wrote the preface 
to the fourth edition of his geology, he expressed his contempt thus : 
"Great importance, " he says, "is attached to the studj^ of fos- 
sil shells; but the character of the animals that inhabited them, 
of the power they might possess of modifying the form of the 
shell under various circumstances, has scarcely been thought of. 
Some French conchologists are endeavoring to establish the doc- 
trine that fossil conchology, independent of the succession and 
stratification of rocks, is the only true basis of geology; and a 
trifling ditference in the form of a shell, is deemed sufficient to 
constitute a new species, and to warrant the most important con- 
clusions respecting the age of the rock formations. ' 
This was sixty years ago, when the general belief was that 
species, are immutable, and therefore that new creation was neces- 
sary to account for distinct species. The geologists recognized 
the importance of species as indication of the age to which the. 
containing rock belonged, and fossils were regarded as particularly 
valuable in classifying and identifying the stratified rocks, but the 
question was raised b}' Deshayes and Lyell — "Is there not a natural 
sequence in the order of the successive species?" Lyell evidently 
did not for several years realize the full import of the question he 
propounded when he spoke of the relative affinity of the species. 
William Lonsdale, in 1839, made a still higher application of 
paleontology, in his determination of the fossils of South Devon- 
shire to be of intermediate age between the Carboniferous and 
Silurian systems, which led Sedgwick and Murchison in the same 
year to propose a Devonian system as of the same age as the Old 
Red system, though containing no fossils of the same species. 
The conditions were these : Murchison had recognized the "Car- 
boniferous limestones" and the following "Coal Measures" in 
northern England containing their characteristic fossils. In the 
Cheviot hills the "Old Red sandstones" were found below them, 
with their fish remains. 
In western England the "Silurian s^'stem" with its marine fos- 
sils was known to run upward into rocks with similar remains, 
considered to be the lower Old Red sandstone. 
