520 



NA TURE 



[Septkmbek 29, 189S 



LETTERS _ TO THE EDITOR 



The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correapond with the writers of, rejected 

 manuscripts intended for this or any other part of NATURE. 

 No notice is taken of anonymous communicaiions.l 



Flow of Water. 



Being away from home at this place, I did not see a copy of 

 Nature of September 15 in time to reply in the next issue to 

 the letter of Prof. Osborne Reynolds. That letter is to a great 

 extent a discussion of a point of considerable interest, viz. the 

 clear border visible in my experiments with air injected into 

 flowing water. 



The discussion is, however, preceded by a statement which, 

 whether intentionally or not, seems to imply that not only had 

 Prof. Reynolds previously with similar apparatus made most 

 of the experiments I have published during the last year or two, 

 but had communicated to me his methods and shown me this 

 apparatus. Apparently, therefore, my humble part has been 

 the production of a certain number of photographs of effects 

 slightly modified from those dealt with by him. 



Now, though questions ot this sort are of little interest, I have 

 no alternative but to reply to all this, because, unfortunately, the 

 real facts of the case as to my indebtedness to Prof. Reynolds 

 have left quite a contrary impression on my mind to that which 

 might otherwise be supposed. 



With brevity in view, I will merely refer your readers to an 

 article in Nature (May 12), which gives a brief outline of my 

 research up to that date. In that article is mentioned and duly 

 acknowledged the only point for which I am indebted to the 

 writings of Prof. Reynolds, viz. the idea of the two manners 

 of motion of water, so ably worked out by him in the Philo- 

 sophical Tran'sactions of the Royal Society. 



Beyond this I cannot recall a single idea, communicated 

 verbally or otherwise, which I owe to Prof. Reynolds, and I 

 certainly have never seen or heard of any other appliances which 

 bear the remotest resemblance to those I have designed and 

 used. 



If the foregoing simple statement of fact is not sufficient, I 

 am quite prepared to enter into the subject more in detail, 

 although I should regret to have to do so. 



My reply to the other portion of the letter will be rendered 

 much more clear by means of diagrams, and I will therefore 

 defer my answer to it until I return to work at Liverpool. 



H. S. Hele-Shaw. 



South Beach Hotel, Troon, N.B., September 26. 



A Request for Zoological Literature. 



I WISH to ask my fellow zoologists, especially those on the 

 I continents of Europe and America, to be kind enough to send 

 me, for our library here, separate copies of their papers and 

 memoirs on zoological subjects. Here, in New Zealand, a 

 naturalist is not only isolated, but has no efficient supply of 

 current zoological literature ; the nearest library containing 

 modern periodicals being Sydney— a week's journey. The 

 museum library in Dunedin, though well equipped in some 

 respects (travels and older books), is extremely poorly provided 

 with periodical literature. We take in the English journals 

 and Proceedings of Societies, &c., but we do not purchase a 

 single German periodical (with the exception of the Naples 

 Mittheilungen and the Jahresberichte), and only one French 

 journal, Annales des Sciences naiurelles. 



Hence, we are fearfully handicapped in our research work, 

 and in our efforts to keep abreast of zoological advances. Out 

 of sight, here, is to be out of mind to a great extent ; and I 

 would earnestly ask my colleagues in Europe and America, in 

 their kindness, to help to remedy this disadvantage. Even if 

 we wish to purchase a work in Europe, it takes at the very least 

 three months before we can obtain any reply to our orders, and 

 more usually four or five months intervene. 



You dwellers in and near cities and large libraries cannot 

 appreciate this great inconvenience. 



W. Blaxland Benham. 



Dunedin, New Zealand, August 14. 



The Movement of Encke's Comet. 



In Prof. Poincare's paper on the "Stability of the Solar 

 System," the statement is made that "astronomers have only 

 been able to explain the movement of Encke's comet by sup- 

 posing the existence of a resisting medium." 



It may be of interest if I state that in a paper published in 

 the Astrophysical /ournal for January 1896, I have shown that 

 the movement of Encke's comet may be explained by the 

 application of well-known physical laws, which have been 

 verified experimentally by a number of physicists, and that no 

 suppositious resisting mediums are necessary. It is also of 

 interest to note that the same phenomena which explain this 

 change of rate also explain the other cometary phenomena, such 

 as the formation of cometary tails, the curious bridge in Biela's 

 comet, and enable us to predict that comets are unstable bodies 

 and must all ultimately split up into swarms of meteorites, the 

 fragments continuously separating from each other. 



I might also call attention to the fact that since, according to 

 this theory (which has so far accounted for all the facts known 

 without assuming any premises except well-known properties of 

 rnatter), a comet can be used as a gigantic absolute electrometer 

 (its tail being the index) for measuring the electrostatic potential 

 of the sun and planets, accurate observation of the curvature 

 and spectra of comets' tails are much to be desired throughout 

 their whole period of visibility, 



Reginald A. Fessenden. 



Western University of Pennsylvania, September 3. 



NO. 1509, VOL. 58] 



Stereochemistry and Vitalism. 



When listening to Prof. Japp's stimulating presidential 

 address, I could not but wish that he had pursued his subject 

 further and inquired into the antecedents of the life-made carbon 

 compounds. 



These are probably formed in the first place, not as com- 

 pounds of only C, H, and O, but rather as constituents of a 

 large molecule which has nitrogen as its centre. The growth 

 of the C, H, and O groups depends on the lability of N com- 

 pounds, i.e. their proneness to transfer matter and energy. If, 

 then, the formation of the said carbon compounds is controlled 

 by the nitrogen, whose atoms (with a valency alternating 

 between 3 and 5) are asymmetrical or have a symmetry different 

 from that of the carbon atoms, does this peculiarity of the nitrogen 

 determine the asymmetry of the resulting carbon compounds ? 



F. J. Allen. 



Mason University College, September 24. 



A White, or Milky Sea. 



I left Bombay for England in January 1881, on board the 

 P. and O. s.s. Sumatra (Captain Briscoe), and on February i, 

 the vessel being then in N. lat. 14° and E. long. 53^ (not far 

 from the position described by your correspondent) had an op- 

 portunity of witnessing the phenomenon known as the " Milky 

 Sea," rarely seen except in these waters. The following 

 extract from my book, " An Engineer's Holiday," describing 

 and explaining the appearance, may interest Mr. Barrett : — 



"The whole ocean, from the ship to the visible horizon, 

 looked as if it were covered with snow, whose surface evidently 

 shone by the reflected light of the sky, for Venus, being very 

 bright, threw a distinguishable line of radiance across it, while 

 the phosphorescent crests of waves were now and then seen 

 breaking above the layer of shining matter which overlaid the 

 water. 



" A current, always encountered north of Socotra, set the 

 ship, on the day in question, fourteen miles to the northward of 

 her course. This stream was crowded with large medusjs, 

 visible not only during the day, but also at night, when, being 

 themselves non-luminous, they appeared as whirling black discs 

 in the general phosphorescence of the ship's wake. The ship's 

 officers fully believed that this current brings with it, besides 

 jelly fish, enormous quantities of decayed and phosphorescent 

 matter, to whose presence they attributed the appearance of the 

 'Milky Sea.' 



' ' The fact, however, that the seeming snow reflects light, and 

 is broken through by quite small waves, disposes of this explana- 

 tion, and we soon convinced ourselves that the phenomenon is 

 really due to a thin layer of mist lying on the water, exactly 



