PREFACE. 



This book is intended as the first of a series of hand-books 

 of local geolog\', which treat the subject with special reference 

 to the needs of the student. The advantage of beginning the 

 stud\' of geology with the special consideration of a selected 

 field, instead of the general text-book stud}^ must be 

 apparent, even though it seems like a complete inversion of 

 the normal order of procedure. 



In order that the student who comes to the field without 

 a preliminary^ training in geology may take up the subject 

 intelligenth^ the first portion of the introductory chapter of 

 Part I. is devoted to a brief consideration of the elementary 

 geological principles involved in the structure of the region 

 under consideration. Hence no apology is needed for the 

 introduction of such matters here. In chapters one and two 

 the eight sections of the most important portion of the 

 gorge of Eighteen Mile Creek and those of the Lake Shore, 

 are considered in detail. Lists of fossils found in the various 

 beds are not given, but such lists will be found in the 

 author's paper on the "Faunas of the Hamilton Group of 

 Eighteen Mile Creek and Vicinity."* As far as this guide 

 treats of the Hamilton group, it is based directly on that 

 paper, and constant references are made to it in the text. 



In chapter three of Part L, an attempt is made to present 

 in popular form the succession of geological events in this 

 region, as revealed in the sections described in the earlier 

 chapters. 



*16th Ann. Kept. N. Y. State Geologist for 1896, Albany 1898 (in press). This 

 paper has precedence over the present one in date of communication. 



