PREFACE 



TO THE SECOND KDITION 



A i the request of the Lords of the Committee <>t Privy 

 Council on Education I gave, in the month of August, 

 1876, at South Kensington, two lectures upon geological 

 m.ips and instruments of surveying. These lectures 

 formed part of a series designed for teachers, and in 

 illustration of the Loan Collection of Scientific Instru- 

 ments at that time exhibited. Treating the subject 

 allotted to me in what seemed likely to prove the most 

 useful manner, I dwelt more specially upon the methods 

 of observation requisite in ordinary field-geology ; and 

 endeavoured to show how, by the practice of these 

 imthods, geological maps and sections, representing in 

 condensed form the facts established by field-work, 

 could be constructed. The lectures were published in 

 pamphlet form later in the autumn of the same year. 

 A large impression having been sold, and the work 



