XC REPORT — 1871. 



" would bo regarded by our contemporaries and by posterity as a fitting 

 " enterprise of a maritime people, and a worthy achievement of a nation 

 " which has ever sought to rank foremost in every arduous and honourable 

 " undertaking." An immediate result of this lleport was that the enterprise 

 which it xjroposed was recommended to the Government by a joint Committee 

 of the British Association and the lloyal Society with such success, that 

 Capt. James Eoss was sent in command of the ' Erebus ' and '■ Terror ' to 

 make a magnetic survey of the Antarctic regions, and to plant on his way 

 three Magnetical and Meteorological Observatories, at St. Helena, the Cape, 

 and Yan Diemen's Land. A vast mass of precious observations, made 

 chiefly on board ship, were brought home from this expedition. To deduce 

 the desired results from them, it was necessary to eliminate the disturbance 

 produced by the ship's magnetism ; and Sabine asked his friend Archibald 

 Smith to work out from Poisson's mathematical theory, then the only avail- 

 able guide, the formulae required for the purpose. This voluntary task 

 Smith executed skilfully and successfully. It was the beginning of a series 

 of labours carried on with most remarkable practical tact, with thorough 

 analytical skill, and with a rare extreme of disinterestedness, in the intervals 

 of an arduous profession, for the purpose of perfecting and simplifying the 

 correction of the mariner's compass — a problem which had become one of 

 vital importance for navigation, on account of the introduction of iron ships. 

 Edition after edition of the ' Admiralty Compass Manual ' has been pro- 

 duced by the able superintendent of the Compass Department, Captain 

 Evans, containing chapters of mathematical investigation and formulaj by 

 Smith, on which depend wholly the jsractical analysis of compass-obser- 

 vations, and rules for the safe use of the compass in navigation. I firmly 

 believe that it is to the thoroughly scientific method thus adopted by the 

 Admiralty, that no iron ship of Her Majesty's Navy has ever been lost 

 through errors of the compass. The 'British Admiralty Compass Manual' 

 is adopted as a guide by all the navies of the world. It has been translated 

 into llussian, German, and Portuguese ; and it is at present being translated 

 into French. The British Association may be gratified to know that the 

 possibility of navigating ironclad war-ships with safety depends on applica- 

 tion of scientific principles given to the world by three mathematicians, 

 Poisson, Airy, and Archibald Smith. 



Eeturning to the science of terrestrial magnetism, we find in the Eeports 

 of early years of the British Association ample evidence of its diligent culti- 

 vation. Many of the chief scientific men of the day from England, Scotland, 

 and Ireland found a strong attraction to the Association in the facilities which 

 it afforded to thom for cooperating in their work on this subject. Lloyd,Phillips, 

 Eox, Eoss, and Sabine made magnetic observations all over Great Britain ; 

 and their results, collected by Sabine, gave for the first time an accurate and 

 complete survey of terrestrial magnetism over the area of this island. I am 

 informed by Professor Phillips that, in the beginning of the Association, Her- 

 schel, though a '•' sincere well-wisher," felt doubts as to the general utility and 

 probable success of the plan and purpose proposed ; but his zeal for terrestrial 

 magnetism broiight him from being merely a sincere well-wisher to join actively 

 and cordially in the work of the Association. " In 1838 he began to give efi"ec- 

 " tual aid in the great question of magnetical Observatories, and was indeed 

 " foremost among the supporters of that which is really Sabine's great work. 

 " At intervals, until about 1858, Herschel continued to give effectual aid." 

 Sabine has carried on his great work without intermission to the present 

 day ; thirty years ago he gave to Gauss a large part of the data required 



