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SECTION III. 



REPORT ON THE RESULTS OF THE MAGNETIC SURVEY OF 

 FUNAFUTI ATOLL BY THE OFFICERS OF H.M.S. "PENGUIN," 1896.* 



By Captain E. W. Creak, R.N., F.R.S. 



The following extract from the instructions for the magnetic survey of Funafuti Atoll 

 forms the keynote to the objects to be attained, and the subsequent conduct of the 

 observations made there : "A magnetic survey of Funafuti is considered to be of 

 importance not only in the interests of terrestrial magnetism, but in its bearing upon 

 the geological investigation to be made there." 



Previously to the " Penguin's" visit our acquaintance with the magnetic elements at 

 Funafuti was confined to a fairly accurate knowledge of the declination, an element 

 which can be easily obtained with sufficient precision by our ships equipped with the 

 ordinary instruments of navigation. The inclination and horizontal force were only 

 approximately known, being deduced from observations made some hundreds of miles 

 distant. There was, consequently, ample need for observation. 



A reference to the accompanying maps (p. 34) shows that the numerous islets of the 

 atoll surround a large expanse of water, extending about 13 miles in a north and 

 south direction, and 9 miles in breadth at its widest part, and studded with numerous 

 coral reefs. It was, therefore, important that this large area, in which possible local 

 magnetic disturbance might be found, should not be neglected. Hence the supply of 

 the Fox dij) and intensity apparatus for observations on a raft capable of being 

 moved to any part of lagoon. 



The following is a list of the instruments employed in the survey :■ — 



1. For absolute observations on land : 



Unifilar magnetometer, No. 25. 

 Barrow's dip circle. No. 34. 



2. For relative observations on the raft : 



Fox dip and intensity apparatus. 



3. For differential observations of the declination : 



A portable difierential magnetometer. 



* Forwarded to Sir W. J. L. Wharton, K.C.B., F.R.S, Hydrographer to the Admiralty. 



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