Jan. 14, 1886] 



NATURE 



247 



even a misleading guide. Now that the difficuUy has 

 been grappled with and conquered, we have half learned 

 to forget the magnitude of the peril. But for the scien- 

 tific and practical progress due to the labours of Capt. 

 Evans and Archibald Smith we might almost with ad- 

 vantage have thrown all our compasses overboard. The 

 attraction due partly to the inherent and partly to the 

 induced magnetism of iron ships, and especially of plated 

 ships, was so violent as to induce in some vessels, in cer- 

 tain positions, errors of two, three, or four points of 

 compass indication. Something had been done to explain 

 the causes of the mischief and to suggest palliatives. 

 Famous old Flinders, at the beginning of the century, 

 had spelt out the mystery so far as it was disclosed by 

 the wooden ships of his time, but he had to deal with com- 

 paratively minute eiTors due to induction alone, and was 

 never brought face to face with the stupendous difficulty 

 which iron shipbuilding and iron ship-plating, afterwards 

 created. The late Astronomer-Royal had done good and 

 sound work in the earlier days of iron, but much more 

 was needed to overcome the serious trouble which the 

 newer types of mercantile and still more of naval vessels 

 threatened to bring upon us. 



It was at this critical epoch that Capt. Evans and 

 Archibald Smith began to work together. Years of 

 experimental labour and mathematical research went to 

 the production of the " Admiralty Manual on Deviations 

 of the Compass ''—a book perhaps as perfect in its kind 

 as a book could be. It is hard to do justice to the 

 elegance of the mathematical handling, and, above all, to 

 the happiness of the graphic methods which are found in 

 the Manual, without seeming to indulge in extravagant 

 laudation. An enthusiast in such matters once pro- 

 nounced it a piece of lovely work, and one need not be 

 an enthusiast to appreciate all that the epithet was meant 

 to carry. Capt. Evans would have been the last to deny 

 that the larger part of the purely theoretical investigation 

 was due to his brilliant fellow-worker. Indeed his modesty 

 often prompted him to claim less than his fair share of 

 the credit due to both. The subject was one which 

 called for the combination of practical sagacity and ex- 

 perience with refined scientific method — and if Archibald 

 Smith was the stronger on the one side, Capt. Evans was 

 his master on the other ; nor was either of them without 

 large powers, even in the special department of their 

 joint labour in which he owned the supremacy of his 

 friend. It was an undertaking which called for the united 

 effort of just two such men as were fortunately brought 

 together to do it, and the result has been a triumph to 

 England and a blessing to the world which will preserve 

 the memories of its authors as long as the ocean remains 

 the highway of Englishmen and of the world. 



The death of his old colleague did not abate the zeal 

 of Capt. Evans, and few years pissed since that time 

 without some notable addition from the hands of the 

 Hydrographer to our existing stock of experimental know- 

 ledge and scientific theory upon the subject which he 

 had made his own. Much of his work will be found in 

 the PJiilosopIncal Transactions of the Royal Society, 

 and in 1870 he published an elementary manual supple- 

 mentary to the Manual ; both these works have been 

 freely translated on the Continent, and are the acknow- 

 ledged text-books in our own and foreign Navies to the 

 present time. 



The various steps of Evans's work may thus be 

 stated : — 



In 185S a Chart of Curves of Equal Magnetic Decli- 

 nation, compiled by him for that epoch, was published by 

 the Admiralty. This chart appeared most opportunely, 

 for, with compass errors growing in amount and com- 

 plexity, the mariner was by means of it enabled to 

 ascertain in any part of the navigable world how far his 

 compass deviated from the magnetic north. 



In 1859 he read a paper on the magnetism of iron ships 



at the Royal United Service Institution. This was 

 valuable resume of all that had been hitherto done in 

 order to obtain a knowledge of the magnetism of iron 

 ships and the treatment of their compasses. He also 

 communicated some results of Archibald Smith's method 

 of analysis as applied to the errors of the compass found 

 in H.M. ships. 



Evans's next paper consisted of a Report to the Hydro- 

 grapher of the Admiralty on Compass Deviations in the 

 Royal Navy. It treated of the magnetic character of the 

 various iron ships in the Navy, and also of the Great 

 Eastern steamship. The results of this paper were (i) to 

 show the best direction for building an iron ship ; (2) the 

 best position for placing her compass ; (3) the various 

 sources of error affecting a compass under favourable 

 conditions. This report was communicated to the Royal 

 Society, and published in their Transactions in i860. 



In 1861 he read a paper of similar import before the 

 Institute of Naval Architects. 



Reference has already been made to his work on the 

 Great Eastern, and an important result of it was the ex- 

 perimental investigation which he was led to make as to 

 the cause of the abnormal errors of the compasses in that 

 vessel, proceeding from the application of Airy's system 

 of magnet and soft-iron correctors when long single- 

 compass needles are used. 



With Evans principally as an experimentalist and 

 Archibald Smith as the mathematician, a valuable paper 

 on the proper length and arrangement of the needles on 

 a compass card, together with exact information as to the 

 proper arrangement of magnet and soft-iron correctors 

 with respect to it, was presented to the Royal Society in 

 1861, being the result of the joint work of those ardent 

 investigators into the compass question in iron ships. 



Commencing with this latter paper, we find Evans and 

 Smith as we have said above, generally working together, 

 and under their joint editorship there appeared in 1862 

 the first edition of the " Admiralty Manual for Deviations 

 of the Compass." The introduction, however, of armour- 

 plated ships soon rendered a new edition necessary, and 

 in 1863 it was published. This work was again revised 

 in 1869, and became the text-book of the world .on the 

 important question of the deviations of the compass in 

 iron ships of whatever form, being translated into all the 

 principal European languages. 



In 1865 Evans and Smith produced another important 

 paper on the " Magnetic Character of the .Armour- 

 plated Ships of the Royal Navy," which was published in 

 the Phil. Trans. Roy. Soc. The novel; v of the form of 

 ships thus discussed as regards their mignetic character 

 caused the results to be of more than usu-jI interest, and 

 showed with what degree of confidence compasses might 

 be placed in positions where both helmsman and officer 

 might have armour protection. 



The practicability of determining the magnetic co- 

 efficients without swinging, and also of ascertaining the 

 heating error without inclining the ship, was aho demon- 

 strated, and has since been largely adopted in the Royal 

 Navy. 



In 1S66 proposals were made by Mr. Evan Hopkins, 

 C.E., to depolarise the iron hulls of ships by means of 

 electro-magnets, and he was allowed by the Admiralty to 

 experiment on the Northuinberland, an armour-plated 

 ship lying in the Victoria Docks. With the increasing 

 difficulty of finding suitable positions for the compass, 

 the prospect of being able to depolarise an iron ship was 

 very attractive. In an able paper, however, read before 

 the Royal Society in 1868, Evans showed that, so far 

 from the hull of the Northumberland Ijeing depolarised, 

 a portion of it was only temporarily, and therefore 

 dangerously, polarised, and afterwards returned to its 

 normal condition, thus preventing similar experiments 

 being tried with other ships of the Navy. 



It was only natural that a joint editor of the " Admir- 



