f/n 



NA TURE 



[April lo, 1884 



and already mentioned in these columns. It dealt with the 

 question from a practical and not an electrical point of view, 

 and is so far valuable as presenting a fresh aspect of the question. 

 On the whole the author s conclusions are satisfactory. He con- 

 siders that there is even now a field for electrical launches in 

 cises where the conditions are favourable, such as having a 

 supply of cheap motive power for recharging the batteries ; and 

 that they are pre-eminently adapted for torpedo boats, owing to 

 their being always ready for action, and their complete noiseless- 

 ness when in motion. On the whole the advantages and disad- 

 vantages as compared with the steam-launch are summed up by 

 Mr. Yarrow as follows, beginning with the former : — 



1. Entire absence of noise. 



2. Great cleanliness. 



3. The whole of the boat is available for passenger accommo- 

 dation, the midship or best part of it not being occupied by 

 machinery. 



4. When once charged it is ready for use at a moment's 

 notice. 



The points against it are : — 



1. Difficulty and delay from frequent charging. 



2. Greater first cost. 



3. Greater cost of working in those cases where an engine has 

 specially to be laid down for the purpose of charging. 



The third paper read was on the Vibration of Steam-vessels, by 

 Mr. Otto Schlick, which dealt with the shaking so well known to 

 passengers on screw steamers from the practical and theoretical 

 point of view. It is shown clearly that the phenomenon is merely 

 due to the fact that the ship, considered as an iron girder, has one 

 or more fixed periods of vibration depending on her length, her 

 width, and other dimensions. With regard to the practical 

 means of overcoming such vibrations, it is pointed out that any- 

 thing which causes the engine to run at a different speed, for 

 instance, the putting in of a new propeller, will probably have a 

 favourable effect. The shifting of the screw to a different angle 

 with regard to the cranks is recommended as often giving a 

 good result, inasmuch as two of the forces causing the vibration 

 may be balanced one against the other. An ingenious apparatus 

 for measuring such vibrations is described by the author. 



The morning of April 3 was occupied during the whole period 

 of five hours by the reading and discussion of three papers on 

 the burning question of Stability. One of these, on the Use of 

 Stability Calculations in Regulating the Loading of Steamers, 

 by Prof. Klgar, we print at length. Another, on Cross Curves 

 of Stability, was read by Mr. W. Denny, the well-known ship- 

 builder of Dumbarton. He observes that stability curves are 

 required for at least four draughts of any steamer, viz. the 

 launching condition, the condition completely finished, but with- 

 out any cargo, coals, &c., on board, the fully loaded condition, 

 and the condition with the coals consumed. If the stability 

 curve be also calculated for an intermediate draught between the 

 second and third of these, five points will be obtained at each 

 angle, by means of which a cross curve of stability can be pro- 

 duced. It is therefore of great importance to work out such 

 cross curves and to find a method by which they can be readily 

 constructed from the ordinary curves of stability. A method for 

 doing this with the assistance of Amsler's Integrator has been 

 devised, and when drawn the curves are also represented by 

 means of a solid model. These cross curves are each for a given 

 angle, and have the length of the righting arm varying with the 

 draught or displacement. With such cross curves in number 

 sufficient to cover angles at intervals of 10°, 15°, and 20°, and 

 each ranging through all the draughts from the launched to the 

 loaded condition, ordinary curves at any draught and with any 

 height of centre of gravity can be easily obtained, and with great 

 rapidity. The method employed is fully described, as is also 

 another method due to Mr. Couwenberg. Tables are also given 

 showing the results obtained for the same steamer by the two 

 methods, which, though worked out separately, were found to 

 agree very closely. 



The third paper was on a New Method for Calculating the 

 Stability of Ships, by M. Daymond. This is an elaborate paper 

 of a theoretical character, illustrated with numerous diagrams. 

 It gives the history of the means adopted for calculating sta- 

 bility, especially the method invented by M. Ferranti. The 

 author's own method is an improvement on this. Having made 

 for various ships numerous drawings which showed on the 

 vertical section of the ship, in length and in direction, the arms of 

 the righting levers, for various draughts and inclinations, he con- 

 ceived the idea of joining by continuous lines the extremities of 

 these arms corresponding to the same angle of inclination. 



Taking such angles at intervals of 10°, he thus obtains a curve 

 which he calls the "pantocarene isocline," and from these 

 curves he obtains at once with com]ilete accuracy and for all 

 possible cases the usual curves of statical stability. The paper 

 gives the principal properties of these curves, together with the 

 mode of their calculation and various examples of working. The 

 paper had been translated by Sir E. J. Reed, who may therefore 

 be considered to have lent his authority to the value of the 

 method proposed. The discussion on these ]ia]3ers turned mainly 

 on unimportant and to some extent personal questions, and, 

 though animated, does not need production here. 



On Thursday evening, Ajjril 3, the jnost important paper was 

 one by Mr. James Howden on Combustion of Fuel in Furnaces 

 and Steam Boilers by Natural Draught and by .Supply of Air 

 under Pressure. The object of it was to describe a new l)oi1er 

 on which the author was experimenting, and which, if his 

 account be correct, is likely to realise very important advantages 

 in the way of economy of fuel. The experiments are not con- 

 cluded, but the author considers them to justify him in claiming 

 a most extraordinary economy as compared with ordinary marine 

 boilers. Taking the instance of the Oregon, the latest-built of 

 the swift Atlantic liners, he professes that the coal consumption 

 might be reduced from 31,000 to 19,000 lbs. per hour, with an 

 equal supply of steam and with a diminution in the fire-grate sur- 

 face from 1512 to only 641 square feet. In the discussion which 

 ensued very grave doubts were expressed as to the reality of such 

 a saving, and it would probably have been more wise if the 

 author had completed his experiments before claiming so very 

 large a step in advance. 



The next paper, by Mr. A. B. Broun, on the Application of 

 Hydraulic Machinery to the Loading, iS:c. , of Steamships, gave 

 an interesting account of a complete hydraulic system applied lo 

 all the work required in an ordinary vessel, but did not raise any 

 theoretical questions. A paper was then read by Mr. J. F. 

 Hall, on Cast Steel as a Material for Crank Shafts. The author, 

 who belongs to the well known firm of Messrs. Jessop of Shef- 

 field, advocated the making of these important parts of a ship 

 by the ordinary method of casting steel, without any subsequent 

 hammering or working. His view is that such hammering can 

 never reach the centre of a large mass of steel, such as an ingot ; 

 and that even if it did it would not completely weld up and remove 

 the cavities which are not infrequently found in that region. In 

 fact his view was that forging actually did harm by consolidating 

 the outer layers and preventing them from contracting subse- 

 quently, as the hotter interior shrank in its cooling. By using 

 ordinary methods of casting, and taking care to have a sufficient 

 head or column of metal standing up above the casting itself, he 

 considered that all fear of cavities within the latter was removed. 

 Any unsoundness would be found only within the column, which 

 would of course be cut off when the casting was cool. 



The remaining papers, read on Friday, will not require any 

 extended notice. That of Mr. P. Jenkins, on the Construc- 

 tion of Metacentric Diagrams, was a theoretical paper, dealing 

 with the problem of stability, and chiefly devoted to establishing 

 the following theorem : — " For any position of the centre of 

 gravity the initial righting moment is either a maximum or a 

 minimum when the water plane is so placed that the centre of 

 curvature of the curve of flotation is at the same height in the 

 vessel as the centre of gravity." .\nother contribution to the 

 same problem, that of stability, was read by Mr. S. Benjamin, 

 and described a model or apparatus enabling a shipowner to 

 determine the position of the centre of gravity of his vessel for 

 any loading before she is loaded, and also the alteration of its 

 position due to any subsequent change in the loading. Yet 

 another paper, by Dr. A. Amsler, described the application of 

 the integrating apparatus which bears that name to such calcu- 

 lations as those of the curves already mentioned in Mr. Denny's 

 paper. Mr. J. E. Spence described a form of diagram exhibiting 

 in a simple shape all the data depending on the form of a ship 

 which are required for determining her stability, and also a 

 simple and direct method of graphic calculation for attaining 

 these data. Mr. Thomas Phillips read a paper on the comparative 

 safety of the particiUar class of vessels known as " well-decked '' 

 steamers. These were formerly treated with some suspicion by 

 underwriters, but great improvements have lately been made, 

 some of which were described in the paper, and with these the 

 vessel appears lo be even safer than wh.at are called "flush" 

 ships. Lastly, Mr. A. Taylor described a special instrument 

 invented by him, and called a Stability Indicator, for deter- 

 mining the initial stability and stowage of ships at any displace- 

 ment. 



