April T, 1887] 



NA TURE 



539 



men and trained officers, and provided also that in con- 

 sideration of tlie yearly subsidy their services were to be 

 always at the disposal 'of the State in case of war at a 

 fixed rental to b-; arranged beforehand. A beginning has 

 undoubtedly been accomplished in the arrangements 

 recently concluded between the Cunard and the White 

 Star Lines on the one hand, and the Admiralty and the 

 Post Office on the other, but much yet remains to be 

 done, and we earnestly trust that Sir Nathaniel Barnaby's 

 paper may be brought under the serious notice of those 

 upon whom will devolve in time of war the care of our 

 mercantile navy and the protection of our food supplies. 



M. L. de Bussy, the Inspecteur-Gen<5ral du Genie 

 Maritime in the French Ministry of Marine, read a short 

 paper on the results of a series of trials carried out on a 

 torpedo boat at progressive speeds, in which he called 

 attention to the fact that there is a diminution in the re- 

 sistance of the hull after a certain speed has been passed. 

 This fact was, however, already well known to members 

 of the Institution, the peculiar sinuosities, or humps, as 

 they are called, on the speed and power curves of vessels 

 tried at progressive speeds having been often discussed 

 at previous meetings. When all the causes of resistance 

 to propulsion are separately analysed and expressed by 

 correct formulae, the causes of these successive maxima 

 and minima of resistance will no doubt be clearly 

 intelligible. 



Mr. J. H. Biles, the scientific adviser of the firm of 

 Messrs. J . and G. Thomson, of Glasgow, read an interest- 

 ing paper on the twin-screw torpedo boats, IViboix and 

 Ei Deslructo); constructed by his firm for two foreign 

 Governments. The author first gave full particulars of the 

 dimensions of the boats and engines, and their perform- 

 ances. These vessels were considerably larger than the 

 generality of first-class torpedo boats, the Wiborg being 

 142 feet 6 inches, and the Destruclor 192 feet 6 inches in 

 length. They are both minutely subdivided, the former 

 being provided with 23 and the latter with 39 water-tight 

 compartments, the object being, of course, to enable them 

 to keep afloat as long as possible when exposed to the fire 

 of machine guns. The paper is interesting as showing the 

 most recent tendency in torpedo-boat design. Recent 

 experience in this country and in France undoubtedly 

 points to the conclusion that the older type of first-class 

 boats, though useful enough for harbour defence, are of 

 little or no avail for service at sea. Whether the latest 

 types described by Mr. Biles will fulfil reasonable expecta- 

 tions in this direction is a question which can only be 

 solved ai)ihulatnl<K 'It may be noticed as a curious 

 instance of the skill of modern marine engineers in evolv- 

 ing enormous powers out of engines of limited size, that 

 the Destructor, whose load displacement is only 4-So tons, 

 has developed'over 3800 horse-power, and has made the run 

 of 495 knots from Falmouth to Muros in twenty-four hours, 

 which corresponds to a mean speed of 20'625 knots. 



Mr. Dixon Kemp, a well-known authority on yachting 

 matters, read an interesting historical paper entitled 

 " Fifty Years of Yacht-Building," in which he traced out 

 the gradual evolution of the English and .American types 

 of racing yachts from the commencement of the present 

 reign down to the most recent times. The author brings 

 out very clearly the causes which have led to the adoption 

 of the relatively narrow and heavily lead-ballasted boats 

 which have hitherto found favour on this side of the 

 Atlantic, and the broad, shallow, centre-board yachts 

 peculiar to the Americans. In view of the recent triumphs 

 of the American type, as represented by the Puritin and 

 May/lower, an alteration has been con-idered desirable in 

 the old tonnage rule which taxed the beam so severely. 

 The Committee of the Yacht-Racing Association ap- 

 pointed to report on the subject have recommended the 

 following rule : — 



Pt.,„« _ Length of loadline X sail area_ 

 6000 



The first outcome of the new rule is the Clyde-built yacht 

 7"//?>//i',theprincipal proportions of which contrast strongly 

 with those of the now famous Galatea, as will be readily 

 seen from the following figures : — 



Galatea. 

 Length of loadline . . 87'o feet , 

 Beam extreme . . . . i5'o ,, 

 Draught of water . . . I3'5 ,, . 



T/iistle, 

 . 85 o feci 



• 20-3 ,, 



• H-i .. 



It should be mentioned that in the case of the Thistle 

 the depth of the hold is measured to the bottom of the 

 keel, which is a hollow box intended to hold the lead 

 ballast. The contests, which will doubless take place dur- 

 ing the coming season, between the Thistle and some of 

 the powerful American centre-board yachts, will be watched 

 with great interest by yachtsmen. Whether a contest 

 between a keel-yacht and one fitted with the centre-board 

 is a satisfactory trial of merit is at least open to question. 

 In this connexion it may be mentioned that a yacht like 

 the Mayflower when sailing off the wind can effect a re- 

 duction of 10 per cent, in her immersed surface by hous- 

 ing the centre-board, an advantage which is manifest, 

 especially in the case of light winds and slow speeds. 



A subject of great importance with regard to iron 

 and steel ships is the protection of their bottoms from 

 corrosion. Mr. \'. B. Lewes contributed a valuable paper 

 on the nature and genesis of rust, and on the piotec- 

 tion of plates from its effects It seems now to be 

 generally admitted that the corrosion which distinguished 

 some of the earlier steel-built ships was due to the pre- 

 sence on the plates of mill-scale or black magnetic oxide 

 of iron, which forms, with the metal of the plate, a 

 powerful galvanic couple, and gives rise, in the presence 

 of sea-water, to very rapid pitting or local corrosion. 

 The action is, in fact, similar at the outset to that which 

 takes place between metallic lead and its peroxide in the 

 well-known Plante secondary batteries. At the present 

 time, steel plates are always carefully freed from this 

 magnetic oxide before being worked into the hulls of 

 ships — a practice which has been attended with the best 

 results. Mr. Lewes believes that the protective compo- 

 sitions of the future will be made by dissolving a good 

 sound gum, not easily perished by sea-water, in a volatile 

 solvent, care being taken that neither gum nor solvent 

 give rise to any organic acids. Body will be given to 

 this varnish by finely-divided metallic zinc, which can 

 now be obtained in so fine a powder that it can be used 

 as a pigment. When, in time, the varnish perishes, as 

 it must do from the action of sea-water under pressure, 

 the zinc will set up galvanic action with the hulI-pIates ; 

 but, being the more electro-positive of the two metals, it 

 will corrode, and will thus protect the iron or steel plates. 

 This paper does not deal with the much-vexed subject of 

 anti-fouling compositions — a much larger subject, which 

 the author reserves for a separate memoir. 



Sir Nathaniel Barnaby read a second paper on the 

 subject of fuel-supply in ships of war, which, together 

 with a paper by Mr. Biles, on the comparative effects 

 of belted and internal protection upon the other ele- 

 ments of design of a cruiser, apparently provoked more 

 interest and discussion than any other communication 

 made to the Institution this year. The ships to which 

 Sir Nathaniel Barnaby alluded were the Impcrieuse and 

 U'arspite, belted cruisers, for the design of which he was 

 himself chiefly responsible. These vessels have lately 

 been the subject of much adverse comment both in 

 and out of Parliament. As originally designed, the 

 armoured belt was intended to reach from a height 

 of 3 feet 3 inches above the water-line to a depth 

 of 4 feet 9 inches below it. The supply of coal on 

 which this calculation was based was 400 tons, but bunker 

 space was allowed for an additional supply of 500 tons. 

 During construction various additions were made to the 

 weights of the boilers and the armament, which in their turn 

 involved an increase in the weight of hull, and the net 



