TRANSACTIONS OF SECTION E. 703 



have been published from time to time; and the last, for the epoch 1902, is based 

 upon 8,000 observations. 



There are other contributions to terrestrial mag-netism for positions on various 

 coasts from the surveying service of the Royal Navy, and our ships of war are 

 constantly assisting with their quota to the magnetic declination, or variation, as 

 sailors prefer to call it ; and wisely so, I trow, for have the}' not the declination of 

 the sun and other heavenly bodies constantly in use in the computation of their 

 ship's position ? 



This work of the Royal Navy and the Indian Marine is one of great import- 

 ance, both in the interests of practical navigation and of science ; for besides the 

 equipment of instruments for absolute determinations of the declination, dip, and 

 horizontal force supplied to certain of our surveying-ships, every seagoing vessel 

 in the service CBrries a landing compass, specially tested, by means of which the 

 declination can be observed with considerable accuracy on land. 



Although observers of many other objects may still speak of their 'heritage 

 the sea ' as a mine of wealth waiting for them to explore, unfortunately for mag- 

 netic observations we can no longer say ' the hollow oak our palace is,' for wood 

 has been everywhere replaced by iron or steel in our ships, to the destruction of 

 accurate observations of dip and force on board of them. Experience, however, 

 has shown that very useful results, as regards the declination, can be obtained 

 every time a ship is ' swung,' either for tliat purpose alone, or in the ordinary 

 course of ascertaining the errors of the compass due to the iron or steel of the 

 ship. 



As an example of this method, the cruise of the training squadron to Spitz- 

 bergen and Norway in 1895 may be cited, when several most useful observations 

 were made at sea in regions but seldom visited. Again, only this year a squadron 

 of our ships, cruising together near Madagascar, separated to a distance of a mile 

 apart and ' swung' to ascertain the declination. 



I would here note that all the magnetic observations made by the oiRcers of 

 H.M. ships during the years 1890-1900 have been published in a convenient form 

 by the Hydrographic Department of the Admiralty. 



The fact remains, however, that a great portion of the world, other than the 

 coasts, continues unknown to the searching action of the magnetic needle, whilst 

 the two-thirds of the globe covered by water is still worse ofl". Amongst other 

 regions I would specify Africa, which, apart from the coasts, Cape Colony, and 

 the Nile valley to lat. 5k N., is absolutely a new tieldfor the observer. 



Moreover, the elaborate surveys I have mentioned show how much the results 

 depend upon the nature of the locality. I am therefore convinced that travellers on 

 land, provided with a proper equipment of instruments for conducting a land survey 

 of the strange countries which they may visit, and mapping the same correctly, can, 

 with a small addition to the weight they have to carry, make a valuable contribution 

 to our knowledge of terrestrial magnetism, commencing with observations at their 

 principal stations and filling in the intermediate space with as many others as 

 circumstances will permit. 



The Antarctic Expedition. 



Of the magnetic work of our Antarctic expedition we know that since the 

 ' Discovery ' entered the pack— and, as far as terrestrial magnetism is concerned, 

 upon the most important part of that work — every opportunity has been seized 

 for making observations. 



Lyttelton, New Zealand (where there is now a regular fixed magnetic observa- 

 tory), was made the primary southern base-station of the expedition ; the winter 

 quarters of the ' Discovery,' the secondary southern base-station. Before settling 

 down in winter quarters, magnetic observations were made on board the ship 

 during the cruise to and from the most easterly position attained off King 

 Edward VII. Land in lat. 76° S., long. 152^° VV., and she was successfully swung 

 oif Cape Crozier to ascertain the disturbing elfects of the iron upon the compasses 

 and dip and force instruments mounted in the ship's observatory. 



