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NATURE 



\_yune 6, 1878 



defects of so excellent and comprehensive a work as this 

 is too distasteful to be pursued through more than a 

 single chapter. 



It is impossible to conclude this notice of Mr. White's 

 work, however — which, by the by, is well-indexed and 

 turned out of hand by Mr. Murray in his usual style of 

 efficiency and excellence — without reflecting upon the 

 immense developments which naval architecture has 

 undergone during the present century, is still undergoing, 

 and has yet obviously to undergo. There is not a chapter 

 in this volume of many chapters, which does not abound 

 with illustrations and indications of improvement. 



" Men, my brothers, men the workers, ever reaping something 

 new : 

 That which they have done but earnest of the things that they 

 shall do." 



Take, for a single example, the material of which the 

 naval constructor builds his ships. How recently is it 

 that wood was in universal use ; now far more than 

 nine-tenths of the ships built are of iron. But already 

 iron is being superseded by steel, and a few weeks ago 

 Mr. Martell, the able Chief Surveyor of Lloyd' s Registry, 

 said at the Institution of Naval Architects, " The time 

 has now come when it is said by many others besides the 

 manufacturers that steel can be used with as much con- 

 fidence as iron ; and it is held that whilst the properties 

 of mild steel are in every respect superior to those of iron^ 

 the cost — having regard to the reduced weight required — 

 will warrant the shipowner, from a commercial point of 

 view, in adopting the lighter material." The manufacture 

 of this "mild steel" for ship-building purposes, and 

 indeed for many other purposes, is, as Mr. White 

 states, " mainly due to the efforts of Mr. Barnaby, 

 Director of Naval Construction, who had previously con- 

 ducted most of the experiments on steel made in the 

 Royal Dockyards, and done much to develop the use of 

 the material." By insisting upon the combination of 

 increased strength with great ductility in the material, Mr. 

 Barnaby directed the attention of manufacturers to the 

 great importance of turning their energies into a new 

 direction, and the result has been the production of a 

 most excellent material for the purpose, which can now 

 be obtained in any quantity from several firms. But even 

 these most recent forms of steel seem destined speedily to 

 be replaced by the fluid-pressed steel of Sir Joseph Whit- 

 worth, who, by the application of enormous force to the 

 metal in a molten state, can solidify and make sound 

 castings which contain whatever proportion of carbon 

 may be desired. By pursuing this process through a 

 thousand details, and many years of costly experiment, 

 this distinguished man has given us a material which is 

 as superior to the best mild steel produced otherwise as 

 that is itself superior to the ordinary forms of ship- 

 building iron, and the process promises to carry us to 

 results of far greater importance still. It is perhaps one 

 of the few reflections which should reconcile us to the 

 persistence of mankind in the pursuit of the arts of war that 

 the eager desire to improve guns and war-ships is continually 

 conducting us to collateral and large improvements in the 

 materials employed for the purposes of civilised life — for 

 commercial ships profit no less than war-ships and guns by 

 the improvements of men like Sir Joseph Whitworth, who 

 has himself contributed immensely to the manufacturing 



arts, both directly and indirectly. The fields in which 

 Mr. Froude is labouring are not less prolific than this, 

 while the forms of vessels, and the propelling powers ap- 

 plied to them, are receiving continual improvement. In 

 respect of naval architecture, at least, Tennyson is right ; 

 and that which we have done is but an "earnest" of the 

 things sooner or later to be done. E. J. Reed 



TROPICAL NATURE 



Tropical Nature and other Essays. By Alfred R. 



Wallace. (London: Macmillan and Co., 1878.) 



MR. WALLACE tells us that the luxuriance and 

 beauty of tropical nature is a well-worn theme 

 and that there is little new to say about it, and yet 

 he thinks that none have as yet "attempted to give a 

 general view of the phenomena which are essentially 

 tropical or to determine the causes and conditions of 

 those phenomena. Indeed many very erroneous ideas 

 are commonly entertained about the charms of the tropics 

 and about the brilliant tints of its flowers, and birds, and 

 insects. 



In the first three chapters of this most interesting 

 volume Mr. Wallace treats of the climate of the tropics, 

 of its vegetation, and of its animal life. A fourth treats 

 of the humming-birds as illustrating the luxuriance of 

 tropical nature. The next two enter on the discussion of 

 the nature and origin of the bright colours of animals 

 and plants, showing how far and in what way these are 

 dependent on the climate and physical conditions of the 

 tropics. A seventh chapter contains an account of 

 certain curious relations of colour to locality, which are 

 almost exclusively manifested within the tropical zones, 

 while the next and last chapter tries to explain the pro- 

 bable origin of many of the forms of life now charac- 

 teristic of tropical regions. 



Despite its being a well-worn theme and its want of 

 novelty, Mr. Wallace has succeeded in writing a most 

 interesting volume on the peculiarities of tropical life, 

 and this chiefly from the results of his own long expe- 

 rience of nature in the eastern and western tropics of 

 the equatorial zone, while his theory to account for the 

 diverse colours, the special adornments, and the brilliant 

 hues which distinguish certain male birds and insects — 

 a theory quite opposed to that of Mr. Darwin' s — cannot 

 fail to attract the attention of all interested in this 

 subject. 



Mr. Wallace's account of his theory is perhaps the 

 most important portion of his book ; he finds, on close 

 examination, that neither the general influence of solar 

 light and heat, nor the special action of variously-tinted 

 rays, are at all adequate causes for the many wondrous 

 complexities of colours with which we are acquainted. 

 He would therefore take another view, dividing the 

 colours into groups, as they are protective to the creature, 

 act as warning colours, or sexual colours, or typical 

 colours, or simply as in floras, attractive colours. 



Mr. Darwin' s theory on this subject of colours was that 

 all, or almost all, the colours of the higher forms of 

 animal life were due to voluntary or conscious sexual 

 selection, and that diversity of colour in the sexes is due 

 at least, first of all, to the transmission of colour varia- 

 tions either to one sex only or to both sexes, the difference 

 depending on some unknown law and not being due to 



