214 



NATURE 



IJuly 7, 1 88 1 



As for tliv- little parentlie~is which offended me, I am sorry I 

 noticed it, a d liope Mr. Venn will forgive the passing irritation 

 which it p-'diiceJ. What he means by the words "I knew 

 that he was very an --i jus that the fact should be known," I do 

 not quite understand ; but the matter is too unimportant for 

 further comment. 



With regard to the "crowning triumph" quotation or mis- 

 qu ita'irjn, I can only congratulate Mr. Vena on the adroitness 

 with which he eluded the dilemma in which I quite thought I 

 should place him. In my simplicity I expected that he would 

 answer Yes or No to my question ; but Mr. Venn was not thus 

 to be caught. 



It is but fair to own that the critical remarks which I made on 

 Mr. Venn's book in my lat letter, though perfectly just as far as 

 they go, are somewhat one sided. As I only spoke of points on 

 w-hich he and I differ in opinion it could not well be otherwie. 

 His book contains much other matter which I did not touch 

 upon at all, and of which 1 entertain a very high opinion. His 

 diagrammatic method especially is most ingenious, and his expo- 

 sition of it is lucid and atlr.ictive. The limits of its application 

 in actual practice are, as he himself points out, rather narrow ; 

 but within those limits, and for purposes of illustration and veri- 

 fication, it is undoubtedly an important contribution to the science 

 of logic. Hugh McColl 



Boulogne-sur- Mer, July 2 



How to Prevent Drowning 

 Those who have followed the correspondence commenced in 

 Nature by Dr. MacCormac may be interested in the foUovviug 

 extract from an es-ay, " Pourquoi les Betes nagent naturelle- 

 ment," which occurs oddly e:ioUi^h in a book entitled " Observa- 

 tions sur les Plantes et leur Analogic avec les Insec'es," published 

 at Strasburg in 1741 by Guido Augustin Bazin, a physician of 

 that place : — 



" Lor-qu'un homme qui n'a point appris a nager tombe dans 

 I'eau, il n'y a point de doute que s'il pouvoit tenir son corps 

 dans une position verticale et fixe, et porter ses jambes en avant, 

 comma il fait lorsqu'il marche sur la terre, il ne put nager 

 naturellement aussi bien que, les betes, les habiles nageurs le font 

 souvent pour leur plaisir. Nous connoissons uu peuple enticr qui 

 ne nage pas autrement, ce sont les Hottentots ; voici ce qu'en dit 

 Mr. Kolbe, dans une bonne description qu'il nous a donnee du 

 Cap de b mne Esperance ; — "Aussi faut-il avouer qu'ils (les Hot- 

 tentots) sont les meilleurs et les plus hardis nageurs que j'aye 

 jajiais vu. Leur mauiere de nager a meme quelque chose de 

 frajjpant, et je ne sjache pas qn'aucune nation s'y prenne de la 

 meme fafon. lis nagent tout droits ; leur co\ est entierement 

 hors de I'eau, aussi bien que leurs bras, qu'ils etendent en haut ; ils 

 se servent des pieds pour avancer, et pour se mettre en equilibre, 

 mais je n'ai jamais pu s9avoir comment ils les font jour. Tout 

 ce qu'il y'a de sur, c'cst qu'il, avancent tres vite. lis regardent 

 en bas, et ont jjresque la me ne altitude que s'ils marchoient sur 

 terre ferme.' Mais cette attitude est impossible a un homme qui 

 ne s'est pas point exerce i la prendre, parce que les mouvements 

 de I'eau, et I'incertitude de son corps, toujours vacillant dans un 

 liquide, le tirent a tout moment de la direction verticale, et 

 I'entrainent malgre lui en avant ou en arriere " (pp. 44, 45)- 



W. T. Thiselton Dyer 



Resonance of the Mouth Cavity 

 I HAVE not tried Mr. Naylor's experiment, but from the 

 account which he gave of it I could not see that any novel fact 

 was involved, nor do I now see that the fact of " the different 

 rates of vibration being already in the air " alters materially the 

 conditions of the case. Whether the sounds are produced by 

 the clatter of wheels, the impact of the thumb-nail upon the 

 teeth, or by the vibrating tongue of a jew's-harp, the part played 

 by the mouth-cavity in sel'jcting the notes of a tune is sub- 

 stantially the same. George J. Romanes 



Storage of Energy 



Like many others, I have given much thjught to the accumu- 

 lation of force, and have felt much astonished at the account of 

 Faure's battery, if it is to be sd called, although of course such a 

 development was to be expected from the time that Plante made 

 his. 



I see that men immediately rush to waterfalls, rivers, and tides 

 to obtain the power for accumulation when they leave coal and 



wood ; my ideas are rather in the direction of wind ; and I have 

 often pictured our country covered, like that around Zaandam, 

 with windmills. The wind is not constant, but more so than 

 most of our efficient stream-, and it is found at every spot. The 

 power is quite unlimited, and we can moderate the action of the 

 machinery whenever we obtain the requisite force. Storage has 

 hitherto been required. I have imagined our windmills pumping 

 up water to great reservoirs, but we have not yet learned to 

 make reservoirs for water except at an enormous expense and in 

 unprotected valleys ; other imaginings have come into many 

 minds, but if we have a really true and safe storage, such, as 

 described, the wind will become our fire to warm us, our steam 

 to drive us, our gas to light us, and our universal servant. The 

 wind will drive our-mills, too (except when a fog comes, lasting 

 so long that our stores of power fail), with sufficient storage, in- 

 constancy will cease to trouble us, whilst every valley may have 

 its lights and every mountain-top its beacon, and darkness will 

 scarcely trouble mankind in this new-coming world of light. We 

 have heard of the golden servants of Vulcan and the mechanical 

 slaves of the great Khan. What will be the result when every 

 man has the wind at his command and the lightning at his service 

 by friction, like Aladdin? It seems to me that the wind' is the 

 great power that we shall next use, and that Prince — the power 

 of the air — shall be bound to serve us for at least a thousand 

 years. 



The Dutch have long made windmills, but when over in Hol- 

 land a few years ago examining a little, I was unable to find the 

 books wanted on the subject. 



The fact that coal can be carried will not affs-ct the question if 

 wind is ued. Wind carries itself. We shall seek our power 

 from the heavens instead of the infernal pits, and a race of 

 healthy, ruddy faces will take the place of the blackened and 

 degraded countenances from mines. 



1 wish to show that we have excess of power in the wind. Will 

 this new accumulator, of which 1 Icnow nothing from per- 

 sonal experience, serve us to keep it? To keep it a few hours is 

 a great point. Coal becomes secondary if we accumulate the 

 force of the wind, and Niagara Itself will be no longer wanted. 

 Of course we neod machines to u-e the wind-power. At present 

 coals are cheaper with us ; not so in all parts of Holland, and 

 not so in many other places. However, here we have problems 

 enough to solve ; do not let us throw cold water on the dis- 

 coveries of others, or show, as scientific men so often do, otu: 

 own opinion to be dear beyond the truth among others. 



R. A. S. 



Explanation of the Female Dimorphism of Paltostoma 

 torrentium 



In his paper on " Pallostoma torrentium, eine MUcke mit 

 zweigestaltigen Weibchen" (A'osmos, vol. viii. pp. 37-42)1 ">y 

 brother Fritz Miiller supposes that this species of Blepharoceri- 

 dx originally was blood-suc'^ing, but in later times changed its 

 habits and became fond of flower-nectar. In the males, who need 

 only little food, this change ofhabits an 1 the corresponding change 

 of the mouth-parts was accomplished, my brother supposes, more 

 rapidly and perfectly than in the females, who, maturing eggs 

 and passing the winter, stand in need of more albuminous food 

 than the males do. Whilst therefore in some females of /'alto- 

 stoma torrentium the same change of habits and mouth-parts has 

 taken place as in the males, other females have still more or 

 less continued their oi'iginal blood-sucking habits and preserved 

 their original blood-sucking instruments. 



This explanation given by my brother is not yet proved by 

 any direct observation of Paltostomds habits. He mentions, as 

 an indirect argument for his opinion, that in several Diptera the 

 females have been stated to be blood-sucking, whilst the males 

 take nectar of flowers. It may therefore be worth publi-hing, 

 that in Empis punctata really just the same takes place as my 

 brother's explanation of the female dimorphism in Paltostoma 

 torrentium requires to be supposed : males who exclusively feed 

 on flower nectar, besides females, both enjoying flower-honey 

 and attacking living animals and sucking their blood. Several 

 weeks ago (.May 26) a great many males as well as females of 

 Empis punctata roved on the flowers of havvt'iorn {Cratcegus 

 cxyacantha). The males were exclusively occupied with suck- 

 ing nectar. Of the females some did the same, whilst others 

 attacked, murdered, and consumed the most clever visitor of 

 flowers among all our Syrphidie, Rhingia rostrata. 



Hermann Muller 



