viii PREFACE TO THE THIKD EDITION 



of irregular triangulation may be found interesting and sugges- 

 tive in dealing with cases requiring the exercise of ingenuity 

 to overcome difficulties. The question of co-ordinating the 

 results by triangulation \\ ith astronomical positions is also one 

 that should have special interest for them. 



I am indebted to Captain H. E. Purey-Cust, R.N., for his 

 kind assistance in revising some of the additional matter 

 prepared for this edition ; and to Rear-Admiral W. U. Moore 

 and Captain T. H. Tizard, C.B., R.N., F.R.S., for the benefit 

 of their advice and suggestions on certain points. 



Through the courtesy of the manager of the Times, I have 

 been enabled to make use of articles contributed by me to the 

 tenth edition of " Encyclopaedia Britannica," for which I have 

 to express grateful acknowledgment. 



A. MOSTYN FIELD. 



DuRRAN Lodge, East Sheen, 

 October 27, 1908. 



