Xll 
INTRODUCTION. 
instances in which even the local identity of beds cannot be ascertained 
by their mineral characters and relative position alone, and in some of 
these my opinion will be found to differ from that of the authors of the 
“ Survey,” in consequence of their having rejected the principle of identi- 
fication by the organized fossils, a principle which I consider as the most 
important yet established in geological science, and of which I trust 
that the present work will be found to furnish some new and strong 
confirmations. 
1 cannot omit this opportunity of expressing my sincere thanks to 
the Officers of the Philosophical Societies of Yorkshire, Leeds, Hull, 
Whitby, and Sheffield, for the liberality with which they have opened 
to me their rich and valuable museums; to Mr. Bean, Mr. Williamson, 
Mr. Dunn, and Dr. Murray, of Scarborough ; Mr. Ripley of Whitby ; 
Mr. J. E. Lee of Hull ; Mr. Cook of York ; Mr. Preston, Mr. Salmond, 
Mr. Smith, and the Rev. L. V. Harcourt ; and the proprietors of many 
private cabinets, who have zealously forwarded my views. To those 
friends who have kindly interested themselves in the success of my 
publication, I have endeavoured to prove my sense of obligation by 
devoting myself to render it worthy of their patronage. But there is 
one individual whose constant and considerate benevolence, warm en- 
couragement, and valued participation in my geological pursuits, de- 
mand my highest thanks ; and those only who like me have found 
unexpected kindness and unmerited attention, can fully understand the 
feelings with which I mention the Reverend W. Vernon Harcourt, 
First President of the Yorkshire Philosophical Society. 
