August 21, 1884] 



NA TURE 



401 



Science, which began in a January number the publication of a 

 series of articles by one of the naturalists who accompanied the 

 steamer. 1 Coming from such an authoritative source, we are 

 led to regard these papers almost in the light of a semi-official 

 report, and look to them for at least a correct statement regard- 

 ing the origin of their methods of work, inasmuch as these 

 matters are discussed in some detail, and with evident pride at 

 the completeness of the outfit. That the outfit was complete no 

 one who is at all posted on the subject can deny ; for nearly all 

 of the many improvements introduced by the Coast Survey and 

 Fish Commission prior to 1880 are most faithfully copied, and 

 most heartily praised for their perfect adaptation to the require- 

 ments of research. 



We glance through the several pages of the report for at least 

 some slight acknowledgment on behalf of American inventive 

 skill ; but beyond a brief statement to the effect that the hoisting- 

 engine " was of the same type as that employed by Mr. Agassiz," 

 and that he also " used with good results the common form of 

 beam-trawl," we are left to infer that the entire outfit was of 

 French origin ; and such must be the impression of every one 

 who reads these papers. In fact, in several instances, credit is 

 explicitly bestowed on French inventors for certain of the appli- 

 ances which do not differ in any essential features from the cor- 

 responding American patterns. 



What is to be gained by thus appropriating to the credit of a 

 nation what properly belongs to another and a friendly one, by 

 all the rights of international courtesy, it is difficult to under- 

 stand, and especially so in this age of supposed enlightenment, 

 when every important discovery is carried with lightning rapidity 

 to all parts of the civilised world. The field of marine research 

 is sufficiently broad to engage the entire attention of all the 

 naturalists who have yet entered it ; and the frequent manifesta- 

 tions of jealousy on the part of foreign, and especially French, 

 investigators, which often result in wholly ignoring the works of 

 an able American author, can but retard progress instead of 

 aiding it. 



Proofs of the superior excellence of American methods of 

 deep-sea research may be found in every important scientific 

 library of Europe as well as this country ; and at the two most 

 prominent International Fisheries Exhibitions of the world — 

 those of Berlin in 1880, and London in 1883 — all of the American 

 appliances were displayed, and received the highest awards. 

 They have therefore been made sufficiently well known to esta- 

 blish their merits before the scientific world ; but, as no descrip- 

 tions of them have yet been published for the benefit of the 

 general public, we propose in future numbers of Science to give 

 accounts of their construction, and of the causes which lead to 

 their introduction. Richard Rathbun 



WHY TROPICAL MAN IS BLACK 

 ""THERE are few subjects the explanation of which has taxed 

 A the ingenuity of man more than the existence of extremes 

 of colour in different sections of the human race. Tradition 

 has attributed the dark race to one of three brothers, the other 

 two being progenitors of the opposite hue, without at the 

 same time offering any solution of the variation from a common 

 stock. 



Physiologists have vaguely asserted that a black skin is best 

 suited to a hot climate, but do not attempt to reconcile the 

 fact that a black coat is certainly the least adapted to the same 

 condition. Evolutionists would doubtless say that in those early 

 days when man in the dense forests of the time was fighting his 

 brave struggle of brain against fangs and claws, the dark skin 

 mingling with the shadows of the overhanging foliage gave him 

 a chance of survival ; but this reaches the conclusion that the 

 first men were black, and that all white men proceeded out 

 from these. 



Yet even if this be so, and if the dark skin served only for 

 concealment, why on the burning tablelands and treeless undula- 

 tions of Central and Southern Africa, where there is scarce a 

 bough to shelter him, has man for so many thousand years pre- 

 served a colour which has become the standard of all blackness ? 

 Surely there must be some other explanation of the fact that man 

 beneath the vertical rays of a tropic sun has persisted in maintain- 

 ing a hue of skin which would appear to have the effect only of 

 absorbing and accumulating the intense heat of his surroundings. 

 Some reason why the ryot of India can labour in the plains 



clad only in the scantiest loin-cloth, and why the African can 

 limit his full dress to a few inches of monkey-tails. 



The rapidly accumulating evidence of the practical utility of 

 every peculiarity, and the proofs that nature, by hoarding up a 

 little of each individual advantage through countless generations, 

 has arrived at the best condition for each environment, compel 

 us to realise the fact that in the tropics darkness of skin 

 contributes to survival. 



That this colour will absorb heat more than any other is as 

 true of the skin of a man as of the roof of a house ; therefore 

 ! In- anomaly is reached that in the tropics he is fittest who is 

 hottest, so long as heat is regarded as the only factor in the 

 consideration. But that one cannot live by heat alone is as 

 true of the animal kingdom as of the whole vegetable world. 

 Light, the twin stimulant of life, because perceptible to our 

 consciousness by its action on a specialised nerve, has been too 

 much limited in our conceptions of its influence to that duty 

 only. 



The gigantic processes of nature by which the great vegetable 

 world, past and present, has been built up, the oxygen of water 

 divorced from its hydrogen in the leaves of plants, and carbonic 

 acid resolved into its constituents, were and are accomplished by 

 the light-waves of the sun ; and yet in the animal kingdom the 

 action of these waves upon the eye is held to be almost their 

 sole effect. 



The craning offshoot of a window-plant, the twisted leaves 

 of an indoor flower are sufficient evidence of the resistless power 

 of light, and the proofs of its effect on man are as numerous as 

 those of its action on plants ; the mode only of that action is 

 the mystery, and yet if this can be even partially explained, 

 enough may be attained to show why those in whom a portion 

 of the rays of the glaring tropic sun are blocked at the surface 

 are best adapted for survival beneath its vertical beams. 



As has been expressed by Prof. Tyndall ("Atoms, Molecules, 

 and Ether Waves," Longman's Magazine, Nov. 1S82), "We 

 know that all organic matter is composed of ultimate molecules 

 made up of atoms, and that these constituent atoms can vibrate 

 to and fro millions and millions of times in a second." Nerve 

 is organic matter, and "whether we meet with nerve tissue in a 

 jelly fish, an oyster, an insect, a bird or a man, we have no 

 difficulty in recognising its structural units as everywhere more 

 or less similar. These structural units are microscopic cells and 

 microscopic fibres, the function of the fibres is that of conducting 

 impressions (represented by molecular movements) to and from 

 the nerve cells, while the function of the cells is that of 

 originating those of the impressions which are conducted by the 

 fibres outwards," {vide "Mental Evolution in Animals" 

 Romanes). 



We can conceive then that the way in which a nerve-fibre 

 conveys to a more central nerve-cell an impression from the 

 surface is by rapid vibration of its component molecules. Such 

 vibrations can be rudely originated by contact, pressure, or such 

 like stimuli, till they give rise to feeling, or, if severe, to pain 

 but they can be not only improvised, they can be communicated' 

 The simplest illustration of vibrations being communicated is* 

 when a piano is opened and sung into ; whereupon the string 

 whose tension coincides with the uttered note will take it up and 

 pass it on in sound. If then vibrations were taking place in the 

 immediate vicinity of the sentient extremities of nerves all over 

 the surface of the body, the same would be expected to occur 



The waves of light and heat follow each other at similar rates 

 through the luminiferous ether. 



Man lives at the bottom of a measureless ocean of this subtle' 

 medium, and is, in common with all else in the universe per- 

 meated by it. " When, therefore, light or radiant heat impinge 

 like the waves of sound just adverted to, their waves select 

 those atoms whose periods of vibration synchronise with their 

 own periods of recurrence, and to such atoms deliver up their 

 motion. It is thus that light and radiant heat are absorbed " 

 (Tyndall). 



Is it not from this easily intelligible how heat-waves notify 

 their existence and intensity along the surface fibre to the central 

 nerve cell, and so enable the animal to avoid their action, if 

 excessive, or seek their increase, when deficient. And shall it 

 be said that while the heat-waves are thus received, and 

 responded to, through every instant of existence, their fellow- 

 workers, the waves of light, are practically inert except for the 

 stimulation of the one specialised nerve of the eye ? 



By going from the complicated and compound to the structure- 

 less and simple, the question can be answered in no uncettaii 

 way. 



