240 



NATURE 



[Jan. 15, 1! 



report of the Government Commissioner, Sir E. J. Reed, 

 directed attention to imperfections in this department 

 of shipbuilding practice, and furnished a powerful stimu- 

 lus to renewed inquiry. Valuable results were speed- 

 ily forthcoming in the shape of more complete and gene- 

 ral expositions of the theory of stability than had previously 

 been given : and in a great simplification, which at the 

 same time included an extension, of the system of calcu- 

 lation. One of the most useful portions of the present 

 work is that which describes the improvements thus made 

 in the theory and practice of the subject. 



The modern improvement of the theory is shown by Sir 

 E. J. Reed to be in the direction of considering the varia- 

 tion of stability with draught of water, and the amount of 

 stability a ship will possess at light draughts. The Daphne 

 inquiry showed that the danger of instability which is some- 

 times to be found associated with light draught of water was 

 frequently lost sight of because of a prevailing belief that, 

 so long as a vessel has a high side out of water, and any 

 initial stiffness, she will have a large range of stability. 

 This point is clearly and fully dealt with by SirE. J. Reed 

 in his present work ; and he states a general proposition 

 which underlies it, and which was first enunciated by 

 Prof. Elgar in the Times of September 1, 1883. It is 

 that, if any homogeneous body which is symmetrical 

 about the three principal axes at its centre of gravity be of 

 such density as to float in equilibrium with its lowest point 

 at a depth x below the water, then if the density be altered 

 so as to make it float with its highest point at a height 

 x above the water, the righting moments will be the same 

 in both cases at equal angles of inclination, and, conse- 

 quently, the range of stability and complete curves of 

 righting moments will be the same. Sir E. J. Reed also 

 gives copious extracts and diagrams from a paper read 

 by Prof. Elgar before the Royal Society in March last, 

 in which the variation of righting moment with draught 

 of water is shown not only for symmetrical bodies, but 

 also for floating bodies of irregular form and for an actual 

 ship. These investigations indicate that the effect of 

 lightness of draught upon stability may be as prejudicial* 

 or even more so, than that due to low freeboard. 



Sir Edward Reed deals very fully with the recent practi- 

 cal developments of the subject, and with the improved 

 systems of calculation that have been devised. These have 

 for their primary object the direct construction of curves 

 showing the variation of righting arm with draught of 

 water at fixed angles of inclination. The wedges of im- 

 mersion and emersion are no longer dealt with in 

 the stability calculations. Atwood's formula involving 

 the volumes and moments of the wedges of immer- 

 sion and emersion is discarded, and the following one 

 is employed (see Fig. 1) gz = br - bg sin 6. B R is 

 computed by calculating the under-water volume at the 

 inclined water-line w' l', and its statical moment. These 

 calculations can be made very quickly and easily with the 

 aid of Amsler's mechanical integrator : and the complica- 

 tion involved by dealing with the two separate wedges, 

 and equating their volumes, may thus be avoided. Sir 

 Edward Reed describes the methods put forward by Mr. 

 W. Denny — who appears to have been the first to 

 suggest this important step — Mr. Macfarlane Gray, Mr. 

 Benjamin, and others. 



It is singular that while naval architects in this country 



were thus working out for themselves those extensions of 

 the difficult problem of stability which modern require- 

 ments have demanded with continuously increasing force, 

 the French appear to have been long in possession of a 

 complete and admirable system. So long ago as 1863 

 M. G. Uargnies was making calculations of stability at 

 Marseilles for numerous angles of inclination, and for four 

 or five draughts of water ; and in 1864 M. Reech put 

 forward a most ingenious and perfect method for bringing 

 all the probable stability conditions of a ship into full view 

 and under calculation. The advantages of this method 

 were so striking that it was not long in becoming practi- 

 cally adopted in France, and, in 1870, M. Risbec prepared 

 a paper upon it, together with a calculation form for facili- 

 tating its application. Sir Edward Reed gives a concise and 

 clear exposition of the systems of MM. Dargnies, Reech, 

 and Risbec, together with an example of M. Risbec's 

 calculation form. The investigations of MM. Ferranty 

 and Daymard are also described in detail. The latter are 

 probably better known in this country than any of the 

 others referred to, in consequence of a paper which M. 

 Daymard read upon the subject before the Institution of 

 Naval Architects in April last. 



There is much in this large and important work to 

 which it is hardly possible to refer, still less attempt an 

 adequate discussion of, within the limits of a short review. 

 We shall return to the subject in a future number. In 

 the meantime, all who are interested in this branch of 

 science, and its bearing upon the construction and safe 

 treatment of ships, will do well to refer to the book itself 

 for full and precise information upon the various aspects 

 of the theory of stability and its practical applications. 

 Fundamental principles are clearly described and illus- 

 trated, and may be readily understood by persons possess- 

 ing an elementary knowledge of mathematics. On the 

 other hand, the elegant and extensive investigations of 

 Dupin, Leclert, Guyou, Moseley, Woolley, and others 

 furnish profitable subjects of study for the most advanced 

 of mathematicians. 



{To be continued.) 



OUR BOOK SHELF 



Natural History Sketches among the Carnivora, Wild 

 and Domesticated ; with Observations on their Habits 

 and Mental Faculties. By Arthur Nicols, F.G.S., &c. 

 (London: L. Upcott Gill, 1885.) 

 This little volume of some 250 pages is full of interest : 

 treating somewhat of lions and tigers, it has a pleasant por- 

 tion of a chapter about cats, but the bulk of the volume is 

 devoted to man's faithful friend, the dog. Of the several 

 excellent illustrations we would especially mention the 

 life-like one of a lioness watching its prey, from a drawing 

 by Mr. J. T. Nettleship, which is very full of vigour and 

 muscular force, one of the black-maned African lion, by 

 Mr. C. E. Brittain, and one of Chang, Mr. G. B. Du 

 Maimer's Grand St. Bernard, by Mr. T. W. Wood. As 

 one of the interesting subjects touched on by Mr. Nicols, 

 we may allude to that treating of the sense of smell in 

 dogs. He alludes to this in connection with the habit 

 possessed by some dogs of rolling in decaying animal, or 

 even vegetable, substances. On one occasion Mr. Nicols 

 noticed his retriever vigorously anointing himself by 

 rolling about in a clump of living fungi which emitted a 

 particularly evil smell. This is thought to be an inherited 

 habit, or, as Mr. H. Dalziel writes, " Taste and smell being 



