534 



NA TV RE 



{April 9, 1 8 85 



and on long ocean voyages its effects are felt, not merely 

 in the lessened expenditure of coal, but in the gain in 

 cargo-carrying capacity. Twenty-five years ago an ex- 

 penditure of from 4 to 6 pounds of coal per indicated 

 horse-power per hour was considered good engineering 

 practice. By the introduction of surface-condensers the 

 expenditure was reduced to about 3 to 4 pounds ; by the 

 use of the compound engine with higher steam pressures 

 the expenditure fell to about 1 to 2| pounds ; and now 

 with triple expansion it has been brought nearly to 

 1 A pounds, or less than one-third of the rate common a 

 quarter of a century ago. These are results of which 

 marine engineers may be proud, and which make the ex- 

 tended use of steamships certain. Nor is further progress 

 to be doubted. Much remains to be done in improving 

 the marine border, and Mr. Milton's thoughtful paper 

 on the subject will do good. Attention has been so fixed 

 on the economical use of steam in the engines, that the 

 possible gains by improvements on the generators of the 

 steam have been overlooked to some extend. The em- 

 ployment Oi forced draught" in the stokeholes is 

 becoming so common, that it was to be expected that a 

 discussion would arise upon it. Mr. Robinson read a 

 paper describing a method by which steam yachts might 

 have the combustion quickened by driving air under 

 pressure into the furnaces, but not closing in the stoke- 

 holes as is done in torpedo boats. This paper was not 

 merely interesting in itself, but served the useful purpose 

 of calling forth some valuable statements of experience 

 gained on larger ships. Forced draughts with closed 

 stoke-holes is now becoming a recognised feature in war- 

 ship design. By these arrangements, involving very 

 moderate additions of weight and cost, the indicated 

 horse-power can be increased by from 50 to 60 per cent, 

 above that obtained with natural draught, and the 

 " forcing " of the combustion can be carried on for four 

 or five hours. A very considerable gain of speed is thus 

 possible for a moderate time, and under ordinary working 

 conditions with low speed, the economical expenditure of 

 fuel is possible. In special types of merchant ships 

 forced draught would also prove of great value ; and 

 even in sea-going steamers something of the kind is 

 likely to be done. Trials are already in progress which 

 promise a great economy in the weight and space re- 

 quired for the steam boilers, while preserving economy in 

 coal consumption. A paper by Mr. Linington, of the 

 Admiralty, on the propelling machinery of high-speed 

 ships, gave a considerable amount of information as to 

 recent Admiralty practice ; and another paper by Mr. 

 Joy, described a special arrangement of valve gear 

 adapted for quick-running engines. Upon the efficient 

 working of such gear, and the proper distribution of the 

 steam, very much depends when high piston speeds are 

 accepted, and the weight of machinery reduced. 



Mr. Thornycroft's name will always be associated with 

 the introduction of the modern torpedo boat, in which 

 quick running engines of remarkable lightness in propor- 

 tion to their pow;r are fitted. His paper on a special 

 form of screw propeller suitable for vessels of very shallow- 

 draught and relatively high speed naturally attracted 

 great attention. The fundamental principle of this pro- 

 peller is not a novelty : but Mr. Thornycroft has brought 

 to a practically successful form what has been little more 

 than an experiment in the hands of others. The pro- 

 peller is one which works with a large amount of " slip," 

 but it is associated with a system of fixed "guide-blades" 

 and casings, by means of which the momentum of the 

 water in the propeller race, which would otherwise be 

 wasted, is made to contribute effectively to the forward 

 thrust of the propeller. The net result of the arrange- 

 ment is that for a given total weight of propelling appa- 

 ratus a higher speed can be obtained than is possible with 

 am other propeller yet tried in shallow draught vessels. 



Mr. Parker, of Lloyd's, read a paper on the use of thick 



steel plates for boilers carrying high pressures of steam, 

 with special reference to a case of recent occurrence where 

 a plate fractured badly and in a most unexpected manner. 

 This paper gave rise to one of the most lengthy and inter- 

 esting discussions at the meetings. Steel makers and 

 users of steel mutually benefit by the joint examination of 

 such problems, which will probably become much rarer 

 than they now are as the manufacture advances. The 

 general opinion expressed in the discussion was dis- 

 tinctly in favour of the generally good behaviour of the 

 new material, whose superior strength,.ductility and homo- 

 geneity make it so formidable a rival to the best classes 

 of iron. 



Two papers on riveted joints were well received : the 

 first giving a risumt of recent Admiralty experiments on 

 riveted specimens of steel shipwork ; and the other deal- 

 ing with certain points of importance in the riveting of 

 boiler shells. 



Amongst the remaining papers, one, dealing with the 

 stowage of steamships, contained a mass of valuable 

 facts. Another paper dealt with the possibility of making 

 such a disposition of the coal bunkers in steamships that 

 the consumption of the coal might not prejudice the sta- 

 bility or render large quantities of ballast necessary. A 

 third was a scientific attempt to lay down rules for 

 competitive yacht-rocking — a hopeless task we fear. 



There still remain to be noticed three of the most im- 

 portant papers in which a distinctly scientific method was 

 followed. Undoubtedly the best of these, from the scien- 

 tific point of view, was that contributed by Mr. Watts, in 

 which he examined into the remarkable effects which 

 free water may produce in checking the rolling motion 

 of even the largest ships. Mr. R. E. Froude assisted greatly 

 in the investigation, and exhibited a model in which the 

 behaviour and influence of the free water were admirably 

 illustrated. It seems obvious that by this means much 

 greater steadiness at sea may be insured than is possible 

 with bilge keels or other appliances of that kind. But 

 there is a need for scientific treatment in order to secure 

 the best steadying effects in a safe and practicable 

 form. 



Another excellent paper was that on "A Mechanical 

 Method of Measuring a Vessel's Stability," by Mr. Heek. 

 Here also a model was used, and by a very ingenious 

 device the movements of the centre of buoyancy of the 

 ship represented by the model were accurately and simply 

 determined for all angles of inclination. It is a method 

 which can be used by comparatively unskilled assistants 

 in a drawing office, although its invention is a proof of 

 thorough knowledge of the principles of stability on the 

 part of the inventor. The plan ought to be widely used, 

 and doubtless will be. 



Finally, reference must be made to the only paper 

 contributed by a naval officer, Capt. Noel, in which he 

 attempted to lay down rules of general application for 

 measuring the " fighting efficiencies " of war-ships of all 

 classes and sizes, differentiating their values according to 

 the nature of their speeds, manoeuvring powers, arma- 

 ments, protection, seaworthiness, and other qualities. 

 The task is seemingly a hopeless one, and no general 

 rules can apply. At the same time the paper sets out 

 clearly and succinctly the leading characteristics on which 

 fighting efficiency depends, and in that sense will be of 

 service to the Institution. W. H. W. 



c 



THE EGGS OF FISHES 1 



ONSIDERABLE advances within comparatively re- 

 cent times having been made in regard to our know- 

 ledge of the spawning of fishes, and the treatment of 



1 i liveredlto the Class of Natural History in the 



of St. Andrews, on .November"™, by Prof. Mcintosh. LL.D.. 

 F.R.S. 



