278 



NA TURE 



[July 20, 1893 



this matter to the Transactions of the Institution for details, 

 which were fully set forth by the author. 



Dr. Elgar's paper was largely of an historical nature. The 

 author, who was until lately the Director of Dockyards, is now 

 the chief technical and scientific adviser to the Fairfield Ship- 

 building Company of Glasgow, the largest shipbuilding corpora- 

 tion in the world. This firm has recently constructed the 

 Atlantic liners Campania and Lucania, at present the biggest 

 ships afloat. The paper drew a comparison between the Great 

 Eastern and these modern vessels, which more nearly approach 

 in size the monster ship of nearly forty years ago than any vessels 

 ever constructed. The following table is interesting as drawing 

 a comparison between the past and present ; — 



Length over all 



Breadth moulded 



Depth moulded to upper deck 



Load draught ... 



Indicated horse power 



Gross register tonnage 



Speed at sea (full power) 



These figures show at once the advance in marine science and 

 the extent to which the past naval architects more than antici- 

 |)ated the work we have yet done in the size of ships built ; and 

 it must be confessed the honours appear to rest with the engineer. 

 The Great Eastern was fitted with both screw and paddle 

 wheels, an arrangement which proved a costly mistake. It 

 should be said, however, that the marine engineer has an al- 

 most unlimited field for the exercise of his ingenuity, whilst the 

 naval architect is fettered and bound in the most vital element 

 of design, namely, the draught of water. It is useless to build 

 a ship which can never enter the great ports of the world, and 

 here we have reached a limit of 27 feet. The ship designer 

 waits for the civil engineer to improve the chief harbours of 

 nations before he can exercise to the full the resources which 

 modern science has otherwise placed at his disposal. An 

 addition of another 5 feet to the depth of some of the chief 

 commercial ports would mean an advance in ship construction 

 before which the growth of the last twenty years, great as it is, 

 would be far eclipsed. For this reason it is likely that the 

 bulk of the Great Eastern will be unapproached for very many 

 years. Her length, great as it was, was a smaller proportion 

 to her breadth than in modern ships, and to equal her dis- 

 placement on the proportions of beam and length which are 

 now considered desirable, a modern ship would require to be 

 considerably longer than was the wonderful craft which was 

 the embodiment of such high ambition forty years ago, and 

 >vhich found her most profitable employment in her last days as 

 a show for trippers to the Liverpool exhibition. 



Mr. Ellis described in his paper trials made at the steel 

 works of John Brown and Co., of Sheffield, to show the ad- 

 vantage of a combination of features which the author consider.? 

 desirable in the generation of steam. He uses induced draught, 

 heating of the air supplied for combustion, and Serve boiler 

 tubes. We have never been able to see what ground the sup- 

 porters of induced draught have for claiming the great virtues 

 supposed to exist in drawing the air through the furnace by 

 means of a fan in the chimney, rather than driving it through 

 by a fan in the stokehole. It is easier to grasp the advantages 

 of heating the air supplied for combustion, supposing it is done 

 by heat that would otherwise be wasted, but it is an open ques- 

 tion whether this regenerative process could not be beneficially 

 replaced by heating the feed water to be supplied to the boiler. 

 It is certain that heat from the waste gases or products of com- 

 bustion will be more readily absorbed by water than by air. 

 In regard to the part of the system involved in the use of Serve 

 tubes, there is perhaps less room for doubt as to the advantages 

 to be reaped. The Serve tube may be described as an ordinary 

 boiler tube, having on its interior a number of metal ribs which 

 are formed in one with the tube itself. The object of these is 

 to penetrate the stream of hot gases, often flame, passing from 

 the furnace to the chimney, and thus act as collectors for the 

 heat to be transferred ultimately to the water in the boiler. 

 The principle may be described as that of the Constantine 

 stove inverted. The device appears logical and we can accept 

 the statement that whatever heat is taken up by the metal 

 is readily transferred to water surrounding the tubes ; or, as one 



NO. 1238, VOL. 48] 



speaker during the discussion put the matter, "if we look after 

 the absorbing surface, we know the distributing surface will 

 look after itself." That is true so long as the distributing sur- 

 face is clean, but it is to be feared such a desirable state of things 

 is not often present in steam boilers. Later in the meeting Mr. 

 Blechynden, in his paper, pointed out how even wiping a plate 

 surface with greasy waste on the water side caused the rate of 

 transmission of heat to fall off, and Mr. Durston some months 

 back told us how bad is the inner side of tubes and plates in a 

 marine boiler. However, the Serve tubes appear to have made 

 a favourable impression upon engineers in spite of the difficul- 

 ties in the way of sweeping, &c., which thieatened them at 

 first. The problem of their introduction appears largely to have 

 established itself on a commercial basis. In the tables attached 

 to his paper Mr. Ellis gave details of the trials made. From loj 

 to \o\ lbs. of water were evaporated per lb. of coal from and 

 at 212° Fahr., burning 40 to 45 lbs. of coal per square 

 foot of grate per hour. The temperature of the gases in the 

 smoke box was from 653 to 692° Fahr., whilst after pass- 

 ing through the apparatus used for transferring the heat of the 

 gases to the air supplied for combustion the chimney gases, 

 386 to 391° Fahr., the difference between the two repre- 

 senting the arrestation of heat units by the regenerative appa- 

 ratus, less accidental loss. An analysis of the chimney gases 

 would form a valuable addition to these details, as was pomted 

 out at the meeting. In any case, however, the boiler tested had 

 a much better chance at Messrs. Brown's works than it woald 

 have had on ship-board ; nevertheless, the results may be said 

 to be encouraging. 



Mr. Hamilton's paper on wear and tear in water-ballast 

 tanks was of a very special character, although a most import- 

 ant matter to shipowners. The moral of his investigations 

 may be summed up in keeping boilers well off the bottom, fill- 

 ing tanks right up, and applying good paint properly at sufficient 

 intervals. If it could be managed to thoroughly dry the tanks 

 when empty it would be of more importance than anything 

 else, but it is difficult to see how this is to be done. 



Mr. Blechynden's paper was also of a special character, and 

 gave the results of some very pretty experiments made to deter- 

 mine the problem referred to in the title of his paper. It wottld 

 be difficult, without illustrations, to describe the experiments, 

 but the broad general fact brought to light was, as the author 

 stated, " that the units of heat transmitted through any of the 

 plates per degree of temperature between the fire and water iire 

 proportional to the difference." The inference might be also 

 drawn from the results that the steel plates lowest in carbon 

 were also lowest in conductivity ; but the experiments, as the 

 author said, should be extended to confirm this. 



Mr. Milton's paper on water-tube boilers dealt with the sub- 

 ject of the hour, at any rate from a marine engineer's point of 

 view. The paper described the most prominent types of water- 

 tube boiler now on trial before the engineering world. By the 

 triple and quadruple compound engine we have placed the motor 

 so far ahead of the steam generators that marine engineers must 

 perforce turn their attention to the first source of power on 

 board ship. The introduction of corrugated furnaces gave the 

 boiler a considerable step in advance, and, together with the 

 use of steel as a material for construction, made the advances in 

 marine engineering so well illustrated by Dr. Elgar's compari- 

 son of the Great Eastern and Compania, at all possible. Leaky 

 tubes, however, have set us all back again, and the conviction 

 is growing among engineers that an entirely new departure is 

 required in boiler design. The only thing that offers is the 

 water-tube system, in which steam is generated in a series of 

 pipes containing water and surrounded by hot gases, rather 

 than in a cylindrical shell through which tubes run to convey the 

 products of combustion through their interior from the furnace 

 to the chimney. The water-tube boiler is almost as old as the more 

 ordinary multi-tube (fire-tube) boiler; but unhappily the lament- 

 able failures of a generation ago — in which several lives were lost — 

 threw such discredit on the system that it has been tabooed ever 

 since. We are now beginning to see how to get over the errors 

 of the past, and the great feature now to be solved is the ques- 

 tion of durability. That can only be settled by time ; and it 

 seems possible that the water-tube boiler may creep from 

 smaller to larger vessels until the shell boiler becomes a thing 

 of the past on shipboard ; at least that is the opinion of some 

 marine engineers whose word is entitled to the highest respect. 

 Possibly in the meantime a practical way may be found of 

 generating power in the motor itself without the intervention of 



