414 



NA TURE 



[March 5, 1903 



LETTERS TO THE EDITOR. 



fThe Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

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

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Sir Edward Fry on Natural Selection. 



I ask leave to make a few observations on Mr. Galton's 

 .letter under the above heading which appeared in your 

 issue of February 12. 



In my papers on the age of the inhabited world and the 

 pace of organic change in the Monthly Magazine lor last 

 December and January, I had a passage on the difficulty 

 which appeared to me to exist in conceiving mimetism to 

 have been produced by the gradual accumulation of minute 

 points of likeness. On this Mr. Galton observes that " two 

 objects that are somewhat alike will be occasionally mis- 

 taken for one another when the conditions under which 

 they are viewed are unfavourable to distinction." If by 

 '" somewhat alike " Mr. Galton means have some point of 

 likeness, however minute, then the proposition would refute 

 my objection ; but it would, as I think, be manifestly untrue. 

 If, on the other hand, by " somewhat alike " be meant 

 •a considerable likeness, then the proposition is manifestly 

 true, but leaves unanswered the difficulty on which I have 

 •dwelt, viz. the difficulty of seeing how natural selection 

 could have helped the organism to convert minute points of 

 likeness in the midst of unlikeness into such a preponderance 

 •of likeness as to produce deception. 



Mr. Galton has illustrated his point by the fact that " i " 

 may often be mistaken by the beholder for " 1," " k," or 

 "h." But here he starts with an obvious and consider- 

 able likeness, and the question is, how could that degree 

 of likeness be reached by natural selection? 



Let us take two sheets of paper, the one a tabula 

 rasa, the other covered with a thousand dots arranged 

 so as to produce a highly complicated pattern. Then 

 let dots appear successively, but sporadically, on the 

 white paper in places where there are dots on the other 

 paper, until, in the end, the two papers are indistinguish- 

 able. It seems to me to be obvious that for a long while 

 no eye would mistake the one paper for the other ; but that, 

 as the process goes forward, a point will be reached where 

 an occasional mistake will occur under conditions unfavour- 

 able to distinction. Now I agree that it is conceivable that 

 from this point forward natural selection may operate, but 

 as to the whole interspace between the first minute change 

 that deceives no one to the point of first deception, it appears 

 to me plain that natural selection cannot operate at all. and 

 that the theory of the accumulation of minute variations, 

 therefore, fails to account for the facts of mimetism in 

 insects and other organisms. 



If the two suggestions of sudden and great variation on 

 the one hand, and of the slow accumulation of small vari- 

 ations on the other be considered as the possible explanation 

 of the facts of mimetism, I cannot but think that the latter 

 will be found far more probable than the former ; and there- 

 fore, whilst willingly admitting the great weight to be 

 attributed to the opinion of Mr. Galton on the subject, I 

 remain unconvinced. 



But suppose that on this point I am wrong and Mr. Galton 

 is right, does he not judge my argument with undue severity 

 when he treats it as " so faulty as to seriously compromise 

 the value of the memoir as a whole "? My observations 

 on mimetism are not the basis of my argument, which is a 

 collection of facts which appear to show the existence of 

 sudden and heritable variations. They are a part, and a 

 separate part only, of an argument that the accumulation 

 of minute variations will not account for some known facts 

 attributed to it. The inculpated paragraph mav be struck 

 out of my paper, and all the rest will stand' unaffected. 

 Even if this error, if error it be, has compromised not a 

 single passage only but the whole of my paper, I am glad 

 to find that Mr. Galton is in sympathy with its general 

 purport, and I thank him for the courteous language which 

 accompanies his condemnation of my lapse. Edw. Fry. 



Failand, February 23. 



NO. I74O, VOL. 67] 





The Assumed Radio-activity of Ordinary Materials. 



With reference to Mr. Strutt's recent article and Prof. J.J. 

 Thomson's letter on this subject, may I venture modestly 10 

 urge that it may be well to consider whether the condition 

 set up in air to which attention is directed be not the out- 

 come of the occurrence of a minute amount of chemical 

 change of an ordinary character — whether it be not a sort 

 of Russell effect on an infinitely minute scale, detected by 

 an infinitelv delicate test? Tliat oxidative change is in 

 continual progress, I imagine, is the belief of everyone who 

 has paid the slightest attention to the subject ; and that 

 leaf surfaces— if not waterfalls— are the certain seat of such 

 changes may be regarded as unquestionable. Those of us 

 who require something more than an attitude of papal in- 

 fallibility in proof of a scientific proposition would like to 

 see the old love honourably retired before the new one is 

 accepted in societv. Henry E. Armstrong. 



The Dissociation Theory of Electrolysis. 

 «In a recently published " Text-book of Electrochemistry," 

 by Svante Arrhenius, and translated by Dr. McCrae, I find 

 on p. 114 of the translation the following statements : — 



" Even when working with polarisable electrodes ... the 

 smallest fall of potential is sufficient to cause a current in 

 the liquid. This fact was proved by Buff with currents so 

 small that it was only after months that a cubic centimetre 

 of explosive mixture was obtained. According to this the 

 very smallest force is sufficient to split the molecules of the 

 Grotthus chain . . . Faraday's view is therefore incorrect. 

 The radicles of the salt molecule cannot be held together 

 by a force of finite value." 



The ideas of current and electromotive force are here 

 rather mixed, but obviously the passage refers to a very 

 necessary part of the foundation of the dissociation theory of 

 electrolysis, viz. that a minute E.M.F. can evolve in the 

 free state the ions of an electrolyte the heat of combin- 

 ation of which is considerable. 



On referring to Buff's papers (Lieb. Ann., lxxxv. p. 1 

 and xciv. p. 1), I find no mention of an evolution in the 

 manner described of any explosive mixture whatever ; 

 taking this to mean free oxygen and free hydrogen evolved 

 simultaneously by an E.M.F. less than that of one Daniell's 

 cell. Indeed, towards the end of his second paper, Buff 

 incidentally states that a single cell produces merely a 

 polarisation which almost stops the current. 



Surely in the attempt to found a theory in opposition to 

 that of Faraday some modicum of care should be taken to 

 verify the sources of information. 



In " Outlines of Electrochemistry," by Prof. Harry C. 

 Jones (1901), we find at p. 15 the same kind of statement, 

 that the dissociation theory accounts for, and is founded 

 on, experimental evidence, showing that " a very weak 

 current " can decompose water and set free its constituents 

 simultaneously. Here also the word " current " is used, 

 though " E.M.F." is apparently meant. 



No reference is given, but the statement occurs in a dis- 

 cussion of the well-known Clausius theory. In his de- 

 scription of this theory {Pogg. Ann., ci. p. 338), Clausius 

 certainly does not mention, and apparently did not believe, 

 that any such phenomenon could occur. 



It would be interesting to know if anyone has ever ob- 

 served it. 



At all events, the acceptance of the theory in question is 

 certainly not encouraged by an encounter with such serious 

 errors in the description of experiments put forward as its 

 foundations. J- Brown. 



Analysis of the "Red Rain" of February 22. 



Some of your readers will probably be interested to know 

 something of the nature of the muddy rain which fell here 

 on Sundav, February 22. A sample of the downfall, caught 

 in an open field between 10 a.m. and 12 noon, was brought 

 to me to examine, and particulars of the partial analysis 

 of the suspended matter which the water contained are 

 subjoined. The large percentage of organic matter seems 

 to me to be the most remarkable point in the analysis, and 

 I regret not having had time to make a separate investi- 

 gation of this. A rapid examination of the physical proper- 



