y^ily 2 2, iSSo] 



NA TURK 



>7i 



mentioned. A few facts and figures bearing upon it may 

 nerertlieless be given. It is citimated that a wave with 

 a 4-seconds period and 82 feet long advances at a speed 

 of 12 knots an hour; an 8-seconds -wave 32S feet long 

 has a speed of 24 knots ; a 12-seconds wave 740 feet long 

 a speed of 36^- knots ; and a i6-seconds wave 1,300 feet 

 long a speed of 4Si knots. If the Livadia were steaming 

 at 14 knots against waves equal in speed to her own, she 

 would of course encounter them at a speed of 2S knots, 

 and that is a speed corresponding to a length of wave 

 of about 450 feet, whereas the waves which she would 

 actually be meeting would be but little over 100 feet in 

 length. Again, if we may for a moment imagine her to 

 be steaming at 18 knots an hour, and encountering similar 

 waves, she would of course be meeting them at a speed of 

 32 knots an hour. But a wave of that speed would be 

 nearly 600 feet long, whereas that which she would, under 

 the last hypothesis, be encountering would be only 100 

 feet long, as before. It is obvious, therefore, that so 

 short a ship, steaming at high speeds, would develop con- 

 ditions unknown alike to vessels of low speed (such as 

 sea-going vessels of her small length usually are when 

 steaming against head seas) and to vessels of high speed 

 but of great length. If we take for example the case of 

 •waves about 500 feet long from hollow to hollow, and 

 therefore of a half-length of about 250 feet, it is obvious 

 that whereas a fast steamship 500 feet long would receive 

 the support of a second wave while the crest of a previous 

 one still gave her bodily support, the Livadia is so short 

 as to be capable of steaming down the wave slope, at an 

 angle to the horizon approximately equal to that of the 

 slope itself. If doing this at a speed of 15 knots an hour, 

 or 25 feet per second, with the on-coming wave advancing 

 upon her, as it would be, at 30 knots an hour, or 50 feet 

 per second, it is easy to see that the behaviour of the 

 vessel would be of an unusual kind. We do not give this 

 as by any means the most notable or critical of the cases 

 which might be selected, but it will serve to show that 

 Mr. Froude was not speaking heedlessly when he said 

 that the purely circular ships would tend to "dive," and 

 to indicate that those persons are probably correct who 

 see in departure from the circular form in the present 

 case evidence, not so much of a desire to diminish resist- 

 ance, as of a desire to correct the diving propensities of 

 very short ships. 



And this brings us to notice the steaming qualities of 

 the Livadia. The enormous steam-power with which 

 she is being supplied has naturally excited much notice, 

 and the Times gave an interesting comparison between 

 her power and proportions and those of the SliaJi. It will 

 assist the further ehicidation of the subject if we invite 

 attention to a different kind of contrast, and compare the 

 Livadia with the largest and most poweifulof our finished 

 armoured turret-ships, the Dreadnought. This huge 

 ship, which steams at 14^ knots per hour, although very 

 much more than twice the immersed size (displacement) 

 of the Livadia, has very much less steam-power. The 

 following is a comparison between the two ships: — 



Drcadmvight. Lil'tuiia. 



Length 320 feet ... 235 feet. 



Breadth, eNtreme 64 ,, ... 153 ,, 



Immersed depth of hull (mean) 23 ,, ... 6J ,, 



Displacement 9, loo tons ... 3,900" tons. 



Indicated horse-power 8,200 10,500 



Allowing for the curvature in the fonn of the hull at 

 and near the bottom, we should of course more than 

 double the Livadia's displacement by carrying her sides 

 at the load-water line vertically upwards, and immersing 

 her another 6h feet ; we should probably, by this process, 

 bring her displacement up nearly to that of the Drcad- 

 oiougltt. As between the two ships, all this extra dis- 

 placement is, so to speak, saved in the Livadia, while, as 

 regards the steam power, hers is in excess of that of the 

 Dreadnouglit by mure than 25 per cent. It will be seen 



from these conditions under what immense advantages 

 the experiment of driving a broad and shallow ship very 

 fast is to be carried out in the Imperial Russian yacht. 

 So far as is known, the designer of the Livadia has not 

 promised more than 14 knots of speed; but if we allow 

 her the same speed as the Dreadnought (i4i knots) she 

 will have a large excess of steam power (no less than 

 2,300 I.H.P.) appliel to the propulsion of a hull weighing 

 very much less than one-half the weight of the ironclad. 

 The speed reached by the latter vessel was sustained 

 throughout a six hours'trial. 



As the Shah is a long fine-lined ship, 15 feet longer 

 than the Dreadnouglit and 12 feet narrower," with about 

 the same mean depth, the Dreadnought may be regarded 

 as a considerable departure from her in the direction 

 which has been pursued so very much farther in the 

 Livadia. _ It will be instructive therefore to compare 

 these two_vessels — 



Sluxh. Drcadtwught. 



Length 335 feet ... 320 feet. 



Breadth, extreme S- >> •■■ ^4 >> 



Depth (mean) 23 ,, ... 23 ,, 



Displacement 5,900 tons ... 9,100 tons. 



Indicated horse-power 7. 500 S,200 



Speed l6i knots ... 14^ knots. 



If we compare the performances of these two extremely 

 different ships— different as regards length and breadth, 

 but not as regards depth— we shall find a material reduc- 

 tion in the steaming efficiency of the short and broad 

 ship, but not one of so marked a character as many might 

 anticipate. Applying to both the well-known formula foi 

 comparing displacements, powers, and speeds, viz. : — 

 Speeds X pi^p.; 

 Ind. Il.-pjwer ' 

 we have — 



Shah 195 I Dreadnought 163 



Or, viewing the matter with reference to the midship 

 sections propelled through the water, or to the volumes of 

 the excavated channels, and adopting the Admiralty 

 formula — 



Speed^ X Mid. Sec. 

 Ind. H. -power 

 we have — 



Shah 587 I Dreadnought 480 



Here we have a loss of, say, 16 per cent, upon the per- 

 formance constants as regards displacement, and_ a loss 

 of more than 20 per cent, as regards midship section, by 

 passing from the fine narrow form of the Shall to the 

 broader and bluffer form of the Dreadnought, observing 

 that the loss would probably have been in greater propor- 

 tion had the Dreadnouglit been of no more than equal 

 size or displacement with the SJiah. 



Although the Dreadnought, as compared with the 

 Sliah, advances towards the Livadia type, the advance is 

 but very small indeed, the Livadia being much more than 

 double the breadth of the Dreadnouglit upon a length of 

 75 feet less. We have in the great Russian yacht an 

 experiment lying far outside of all former experience, and 

 ranging itself under no laws or formula; with which naval 

 archite°ts are familiar. But it may be well to exhibit her 

 in the guise of the formula; which we have just employed, 

 and to do this first upon the assumption of a 14 knots 

 speed, and secondly upon that of a speed of 17 knots— 

 the highest, perhaps, which Admiral Popoff has allowed 

 himself to hope for even in his most sanguine moods, 

 and equal probably to that which his ardent disciple 

 and assistant, Capt. Goulaeft', has ever evolved from the 

 most plastic of his calculations— although we must ac- 

 knowledge that we cannot say this with any great 

 confidence in view of the published paper of the latter 



' The DrcadattuM's breadih diminishes by some feet, we believe, at a 

 depth of 6 or 7 feet below the water's surface, but ih'.s wiU un matenally 

 •nterfere'wiih the compariscn ab.ul to be given. 



