PREFACE TO THE FOURTH EDITION 



Another edition of " Hydrographical Sui'veying " being called 

 for, the opportunity is used to make certain minor corrections, 

 and to add, in the form of a supplement, Some important 

 improvements in connection with s5hip sounding and sweeping 

 both by ships and boats. TheSe have been effected during 

 recent years through the ingenuit}^ of the officers whose names 

 are associated in the text with the various devices therein 

 described. 



I am greatly indebted to the Lords Commissioners of the 

 Admiralty and to the Hydrographer, Rear-Admiral Sir J. F. 

 Parry, K.C.B., for access to official reports and permission to 

 jjublish the information contained therein. 



I have also gratefully to acknowledge the contribution by 

 Rear-Admiral F. C. Learmonth, C.B., C.B.E., of a detailed des- 

 cription of the methods employed by him in the course of the 

 Survey of outlying banks in the North Sea. 



To Colonel Sir Charles F. Close, K.B.E., C.B., C.M.G., 

 Director of Ordnance Survey, I desire to express my thanks 

 for the uSe I have been allowed to make of the articles on 

 Rectangular Co-ordinates in his textbook on "• Topographical 

 Surveying." 



A. M. F. 



TWYFORU, 



Hants, 



March 10, 1919. 



