5'6 



NA TORE 



[April 3, 1890 



cally engaged in the design, of ships a new field of research, 

 the investigation of which will enable tfiem to solve 

 some problems which have hitherto been without ex- 

 planation. T hat is, speaking generally — for the influence 

 of longitudinal bending moment on shearing stress has 

 before been investigated by naval architects ; notably 

 by Mr. W. H. White, the Director of Naval Construc- 

 tion, and Mr. W, John. This, however, was many 

 years ago, and in connection with wooden ships with 

 no longitudinal connection between the planking except 

 that supplied by dowells, the friction of the edge?, and 

 the ■' anchor-stock " shape of the pieces. It will be 

 evident, therefore, that previous investigations must 

 have been of a qualitative, rather than of a quantita- 

 tive, form ; and the world of naval architecture is much 

 indebted to the occupant of the John Elder Chair at 

 Glasgow for putting the problem on a practical quanti- 

 tative basis. 



The paper contributed by Mr. C. E. Stromeyer had a 

 most attractive title, " The Evaporative Efficiency of 

 Boilers " ; and a good many of the working marine 

 engineer members of the Institution, who were acquainted 

 with the thorough manner in which the author follows up 

 all his work, had assembled to hear the paper read, and 

 take part in the discussion. We are afraid it must have 

 been somewhat of a disappointment to several of these 

 gentlemen when they turned over the leaves of the paper 

 as it was placed in their hands, and found that the matter 

 was rather of a suggestive than of a conclusive character. 

 There is so much business to be crowded into the three 

 days' annual meeting of this Institution that it is necessary 

 the papers should be read with despatch ; and we quite 

 sympathize with the engineer whose daily task js of an 

 administrative rather than a contemplative nature, when 

 he is asked to assimilate at a galloping pace two or three 

 pages of mathematical formula; of by no means an 

 every-day character. 



Mr. Stromeyer cor fined himself chiefly to a considera- 

 tion of the relative distribution of efficie; cy in the tubes. 

 He points out that the distribution is governed partly by 

 the temperatures in the combustion-chamber and smoke 

 box, and partly by the resistance of gas in the tubes and 

 this again depends upon the velocity and temperature 

 of the gas, and on the loss of heat experienced by it. 

 Mr. Longridge has found that the coefficient of trans- 

 mission of heat through boiler-tubes or combustion- 

 chamber plates is eleven calories of heat per square foot 

 per hour for every degree F. of difference between the 

 gas and the water : 0*09 1 is the reciprocal value, and is 

 the resistance offered to the flow of heat under the above 

 condition. This resistance is offered when heat passes 

 from one medium to another, as, for instance, from the 

 gas to the metal, from the metal to the boiler scale, or to 

 the water, and it also includes the resistance offered by 

 the metal to the scale. For iron and boiler scale the re- 

 sistances are o"oo202 and 0207 per inch thickness ; so 

 that a clean |-inch plate would offer o 001 resistance; or, 

 if covered with scale one-tenth inch thick, the resistance 

 would be o"ooi + 0*02 1 — 0*022. 



Arguing from these facts the author concludes that the 

 chief resistance, about 80 per cent, is encountered at the 

 surfaces ; and he doubts whether the change of medium 

 from iron to scale, and to water, influences the values very 

 much. The chief difficulty in transmitting heat from the 

 gas to the tubes is want of circulation, or admixture of gas 

 in the tubes. He speaks favourably of draught retarders, 

 corrugated tubes, and ribbed-tubes for the purpose. 



Mr. Stromeyer next refers to the experiments of 

 Haverez (see Ann. du Genie Civil, 1874), by whom it was 

 shown that more heat is absorbed in the fire-box with 

 flaming material than with flameless coke. It is well 

 known that a luminous flame radiates more heat than 

 one which is non-luminous ; and it is for this reason that 

 the latter may not be used in the Siemens-Martin furnace. 



For reasons^iven, Mr. Stromeyer would prefer that, in 

 the formulcTeused by Mr. Longridge for heating boiler 



tubes, the coefficient of resistance should be somewhat 



in 



increased ; say from o'ogi to o-i. This the author works 

 out in detail. We have stripped Mr. Stromeyer's argu- 

 ments of their mathematical aspect, as, howei^er interest- 

 ing the matter may be, we have not space to do it justice. 

 We must refer those of our readers who are sufficiently 

 interested in the subject to the Transactions of the 

 Institution. 



Mr. Macfatlane Gray, of the Board of Trade, was the 

 chief speaker in the discussion which followed. He said 

 he could not pretend at one reading to follow the author 

 in all his reasoning. Mr. Fothergill, who is the superin- 

 tending engineer to a north country line of steamers, 

 gave the meeting the benefit of his practical knowledge 

 upon the subject. Mr. Fothergill is well qualified to 

 speak on the question of the evaporative efficiency of 

 marine boilers, as he has made an especial study of the 

 matter in the actual v/orking of vessels in connection with 

 his well-known researches on the subject of forced 

 draught on ship-board. 



Mr. Brown's paper was one of unusual interest to the 

 members of the Institution. In it he described the most 

 recent development of that beautiful system by which he 

 has so vastly improved the loading and discharging of 

 cargo on steam-ships, and the steering of vessels. The 

 paper was illustrated by several diagrams without the aid 

 of which it would be impossible to make clear the details 

 of the very ingenious methods by which the author has 

 applied his combined steam and hydraulic practice to the 

 purposes named. Briefly stated, it may be said that, in 

 place of the usual deck winches, there is placed at every 

 hatch a derrick, having mounted upon it the hydraulic 

 cylinder which supplies the motive power to lift the 

 goods. The steering motor is placed directly on the 

 quadrant of the tiller, and is actuated from the bridge by 

 means of what the author describes as a telemotor. The 

 transmission of the controlling force which governs the 

 steering motor is through hydraulic pipes ; a vast im- 

 provement on the rattling chains and rods now in com- 

 mon use. In fact the great virtue of Mr. Brown's system 

 is its quiet working. 



Mr. A. Rigg's revolving engine is an ingenious device, 

 perhaps better suited to water than steam. It was fully 

 described in Section G at the last Birmingham meeting 

 of the British Association. 



"Leak Stopping in Steel Ships" was the somewhat 

 misleading title of a rather weak paper by Captain 

 Fitzgerald. The only point the author suggested was 

 that war-ships should be outside sheathed with wood in 

 order that there might be some attachment to which leak 

 stoppers could be affixed. The contention that the swell- 

 ing of wood by moisture that takes place, or used to take 

 place, when a shot cut through the side of an old man-of- 

 war is quite beside the mark, as we suppose no one pro- 

 poses to make the wood sheathing of a modern steel 

 steamer as thick as the sides of our old wooden walls. 

 Three or four inches of elm would do very little swelling 

 when pierced by a modern projectile of any considerable 

 size. 



Mr. T. C. Read's paper on the variation of stresses at sea 

 is another of those contributions which are the despair of 

 the practical naval architect, not over-given to abstruse 

 science, who attends the meetings of his Institution, hoping 

 to take part in the discussions. We are quite at one with 

 the speaker, Mr. Alexander Taylor, who proposed that a 

 rule should be passed compelling contributors to send in 

 their papers sufficiently early for them to be printed and 

 distributed to members before the meetings. The exe- 

 cutive say it cannot be done, but it would be worth 

 trying for a time. 



