312 



NA TURE 



IFeb. 3, 1 88 1 



It is certainly very far from my desire to discourage the present 

 attempts which are being made to clear the atmosphere of our 

 large towns of smoke, and I have recognised the advantages 

 which would result from the adoption of more perfect forms of 

 combustion. In my paper I have simply distinguished between 

 fogs and smoke, and separated them for distinct consideration 

 and treatment, and have at the same time directed attention to 

 some points which ought to be considered before deciding on 

 their prevention. 



With regard to Mr. Russell's difficulty in reconciling the result 

 of the experiments with what is observed with regard to fogs in 

 London, Paris, and other large towns, it appears to me to have 

 arisen entirely from not putting sufficient weight on the all- 

 important influence of the amount of vapour in the air of the 

 different places. It is condensed vapour which forms tlie fog, 

 and dust simply determines whether it will condense in fine- or 

 coarse-grained particle-;. The atmosphere of Paris, compared 

 with that of London, is an extremely dry one, and the air is 

 seldom in a condition to produce fogs. The atmospheres of the 

 other towns mentioned are also drier, some of them very much 

 drier, than that of London. Loudon however will probably be 

 always more subject to fogs tlian other cities on account of its 

 great size, some part of it being always in its own smoke. 



Considered from a different point of view, might not the fog of 

 January 31, 1S80, referred to by your correspondent, be cited in 

 evidence of a conclusion the opposite of that drawn by the 

 writer, and in favour of the correctness of the experimental 

 results? From this point of view the low white fog cleared 

 away because it was formed in the comparatively pure air of 

 the streets, while the higher fog did not clear away because it 

 was formed in the products of combustion The true explana- 

 tion however would rather appear to be, that where the fog was 

 white it was also of less depth than in those places where it 

 "extended high" and mixed with the smoke; and the sun, 

 which was only sufficient to dispel the lesser depth " more or 

 less," would evidently be insufficient to clear away the greater 

 depth. It is h iwever impossible to form any definite idea as 

 to how this par ticular fog conducted itself, without much fuller 

 information as to air-current, &c. 



I have communicated to the secretary of the Royal .Society of 

 Edinburgh a second experimental paper on fogs, with special 

 reference to dry fogs. In this paper the full answer to the latter 

 part of Mr. Russell's letter will be found. John Aitken 



Darroch, Falkirk, January 24 



Professors Exner and Young 



My statement in respect to Prof. Exner's having announced 

 the thermo-electric neutrality 'of a bismuth-antimony pair im- 

 mersed in pure nitrogen, rested upon a note in Nature (vol. 

 xxii. p. 156), and this it seems was based upon a statement in 

 V Ekctrkitc. I have seen those of Prof. Exner's papers which 

 have appeared in the Annalen der Physik, and there is certainly 

 nothing of the sort in them ; but I supposed that it must be 

 contained in some other paper in some one of the numerous 

 other publications to which I have not access here. It never 

 occurred to me, until \\ ithin a very short time, that there could 

 be any mistake as to his having made such an assertion. How 

 or where the error originated I cannot quite understand ; but I 

 trust Prof. Exner will accept ray apologies for my share in its 

 propagation, and that he and all concerned will be satisfied that 

 no misrepresentation was intended on my part. The incident 

 is a good illustration of the extreme care necessary in comment- 

 ing upon the views of another person. C. A. Young 



Princeton, U.S.A., January 12 



The Flying.fish 



It is remarkable that there should still be any doubt as to the 

 facts in connection with the flight of the flying-fish. Dr. 

 Giinther (" Study of Fishes," p. 622), summarising the observa- 

 tion of Mobius, says that "they frequently overtop each wave, 

 being carried over it by the pressure of the disturbed air " (in 

 the open sea!). Again, flying-fishes "never" fall on board 

 vessels "during a calm or from the lee side." At night "when 

 they are unable to see they frequently fly against the weather- 

 Ijoard, when they are caught by the current of air and carried 

 upwards to a height of twenty feet above the surface of the 

 water." Surely the fish going at the rate of at least ten miles an 

 hour would on striking the "weather-board" be dashed, bruised 



and helpless, back into the water instead of coming over the side 

 fresh and vigorous, flapping about on the deck. Except when 

 "by a stroke of its tail" it turns towards the right or left, Mobius 

 concludes that "any deflection from a straight course is due to 

 external circumstances, and not to voluntary action on the part 

 of the fish." 



I have watched flying-fish repeatedly, and have invariably seen 

 ihem fly, or rather glide, over the surface of the sea, and from 

 one to two feet above it, rising gently to the swell when there 

 was no wind, and occasionally turning to the right or left with- 

 out touching the water. 1 do not say that when there is a 

 breeze the tail of the fish may not touch it, but I think that, 

 with the foam and spray of the broken water, it would be very 

 difficult to lie sure of it, and, moreover, if the tail was used the 

 motion would be a jerking one. Mr. Wallace speaks of their 

 "rising and faUing in the most graceful manner," which, 

 although he is referring to another species, applies also to the 

 North Atlantic form (Exoca-tus cvolaus). Mr. Bennett ("Gather- 

 ings," &c., p. 14) says that they "spring from the sea to a great 

 elevation." This is probably in reference to their coming on 

 board ship at night, attracted, it is supposed, by the lights. I 

 believe the pectoral fins are kept extended without any motion, 

 except perhaps as Mr. Whitman,^ a recent observer, says, just 

 when they ri>e from the sea. He gives Soo to 1200 feet as the 

 greatest distance he has seen them fly, and about forty seconds 

 as the longest time out of the water. By what mechanical 

 means they move when out of the water is still to me a 

 mystery. 



I have never known the flying- fish to be pursued by other fish, 

 nor ever seen any bird near them ; indeed few birds are ever 

 seen far from the land north of the southern tropic, where flying 

 fish are most abundant. The dolphin (Corypkcoia) is supposed 

 to be their greatest enemy. I had once an opportunity of seeing 

 one opened — in the West Indies — its stomach was quite full of 

 Orthagoriscus mola, very young, being not quite an inch long. 

 Francis P. Pascoe 



I, Burlington Road, W., Januai-y 21 



Mr. S. Butler's "Unconscious Memory" 



I MUST reply to the review of my booli, " Unconscious 

 Memory," in your issue of the 27th inst., and to Dr. Krause's 

 letter on the same subject in the same issue. 



Mr. Romanes accuses me of having made "a vile and abusive 

 attack upon the personal character of a man in the position of 

 Mr. Darwin," which I suppose is Mr. Romanes' way of saying 

 that I have made a vile and abusive personal attack on Mr. 

 Darwin himself. It is true I have attacked Mr. Darwin, but 

 Mr. Romanes has done nothing to show that I was not warranted 

 in doing so. I said that Mr. Darwin's most important prede- 

 cessors as writers upon evolution were Buffon, Dr. Erasmus 

 Darwin, Lamarck, and the author of the "Vestiges of Creation." 

 In the first edition of the " Origin of Species" Mr. Darwin did 

 not allude to Buffon nor to Dr. Erasmus Darwin, he hardly 

 mentioned Lamarck, and he ignored the author of the "Ves- 

 tiges" except in one sentence. This sentence was so gross a 

 misrepresentation that it was expunged — silently — in later 

 editions. Mr. Romanes does not and cannot deny any part 

 of this. 



I said Mr. Darwin tacitly claimed to be the originator of the 

 theory of evolution, which he so mixed up with the theory of 

 "Natural Selection" as to mislead his readers. Mr. Romanes 

 will not gainsay this. Here is the opening sentence of the 

 " Origin of Species " : — 



"When on board H. M.S. Beagle as naturalist, I was much 

 struck with certain facts in the distribution of the inhabitants of 

 South America, and in the geological relations of the present 

 to the past inhabitants of that continent. These facts, as will 

 be seen in the latter chapters of this volume, seemed to throw 

 some light on the origin of species ; that mystery of mysteries, 

 as it has been termed by one of our greatest philosophers. On 

 my return home it occurred to me in 1837 that something might 

 perhaps be made out on this question by patiently accumulating 

 and reflecting upon all sorts of facts which could possibly hav;- 

 any bearing on it. After five years' work I allowed myself (<> 

 speculate upon the subject, and drew up some short notes ; these 

 I enlarged in 1S44 into a sketch of the conchisious which then 

 seemed to me probable ; from that period to the present day I 

 have steadily pursued the same object. I hope that I may be 

 ■ See Zoologist for November, 1S80. 



