462 



NATURE 



[April II, 1872 



in my reasonings. The casual remark, however, which Mr. 

 Murphy fastens on as involving " a serious mistake in the theory 

 of the trade winds," was almost copied from Article 211 of 

 "Tyndall on Heat;" and as to the matter of fact, I think it is 

 Mr. Murphy, and not Prof. Tyndall or myself, who has fallen 

 into error. Even if I saw any reason why east and west winds 

 should exactly balance each other on the earth's surface, I could 

 not accept Mr. Murphy's position, that if the earth were of any 

 other shape the trade winds could not proceed from the medial 

 line to the extremities. lie assumes that the trade winds are 

 east winds, indcpnulciitly of the shape of the earth, whereas it is 

 just the shape of the earth that makes them east winds. If the 

 earth were a cylinder revolving on its axis, the trade winds (if 

 they could arise under the circumstances) would move directly 

 north and south, and would not be east winds at all ; and I can 

 see no reason why they should not extend to the extremity of 

 the cylinder. See " Tyndall," loe. cit. 



Trinity College, Dublin, April 3 W. H. S. Monck 



Height of Cirrus Cloud 

 It would be interesting if any of the readers of Nature could 

 give some information respecting the usual height of cirrus 

 clouds. Mr. Clement Ley, in his work, "The Laws of the 

 Winds," states— " The time occupied by these clouds in passing 

 from the zenith to 45°, or the contrary, furnishes us with a stan- 

 dard of measurement which is both convenient for simultaneous 

 observations, and also possesses this obvious advantage, that 

 whenever the altitude of the cloud station is at all determinable, 

 none but the simplest of calculations is required iu deducing the 

 actual from the apparent velocity." Granted; but it would 

 have been advantageous had he .shown by an example what he 

 means. For, he goes on to say, " The ordinary range of the 

 actual rapidity of this current is about twice as great as that of 

 the rapidity of the surface winds, for while the latter, at stations 

 most fully exposed to their violence, rarely attain, in Europe, a 

 velocity of 60 or 70 miles an hour, the most elevated clouds not 

 uncommonly traverse a distance of 120 miles an hour, and occa- 

 sionally much more.'' Coupling this with the next statement — 

 " I have only once or twice observed an actually motionless cirrus 

 cloud, and it is on rare occasions that an hour is occupied in 

 passing from the zenith to 45''," let me ask, what would be the 

 vertical height of such a cloud ? R. Strach.i.n 



Low Conductivity of Copper Wire 

 As one of very numerous instances which have come under 

 his notice. Sir WiUiam Thomson desires to make known the 

 following case of the employment of inferior copper wire in the 

 construction of electrical apparatus. He received lately from a 

 Glasgow bell-hanger a large quantity of cotton-covered copper 

 wire, which was being largely used for the coils of electric bells, 

 and upon having it tested very accurately by means of his new 

 Multiple Arc Conductivity Box, its resistance per metre-gramme 

 was found to be no less than 0-439 of a P.. A. unit ; that of 

 ordinarily good copper wire for such purposes being about 0'l6 

 of a V>. A. unit. ' J- M. 



A Pelagic Floating Fish Nest 

 Among other rarities which I have been fortunate enough to 

 procure since my arrival in tlie Bermudas, is a pelagic fish nest, 

 similar in most respects to that \shich Agassiz has so recently 

 described, and which was obtained by the American Expedition 

 in the Gulf Stream in December last, while on the voyage to 

 the West Indies. As I am very busy at present preserving and 

 packing specimens, and the mail steamer nearly due, I have 

 only time to send you (by way of St. Thomis) a brief description 

 of my nest, which has been preserved in diluted alcohol. It was 

 taken from a mass of gulf weed {Fiiciis natans) blown ashore 

 about a month ago. This weed, by-the-bye, has been especially 

 abundant about the Bermudas during the present winter, 

 thousands upon thousands of tons having been cast ashore by 

 the waves during the stormy Aveather which has prevailed. The 

 size of the whole mass is about eight inches by five as it hangs 

 suspended, the former measurement being its depth. The weed 

 is thicker at the top, and is woven together by a maze of fine 

 elastic threads, affording a raft, fiom which depends the cluster- 

 ing mass of eggs, which I cannot illustrate better than by asking 

 your readers to imagine two or three pounds of No. 7 shot 



grouped together in bunches of several grains, and held in 

 position by the elastic thread-work previously mentioned. These 

 threads are amazingly strong, especially at their terminal bases 

 on the fucus sprays, where several are apparen-ly twisted together 

 like tlie fibres of rope, and are admirably adapted to hold the 

 mass in a position where it must always be subject, more or less, 

 to violence, from the continued agitation of the waves in these 

 stormy latitudes. The sea-weed is not only on the summif, but 

 sundry sprays are interwoven with the mass of eggs, thereby 

 rendering the fabric still more solid and secure. It is truly a 

 wonderful specimen of Nature's handiwork ; a house built with- 

 out hands, resting securely on the bosom of the roUmg deep. 

 J. Matthew Jones 



"An Odd Fish" 



Some short time ago I observed in one of the daily papers an 

 account of " an odd fish " which had been captured, and described 

 by Prof. Agassiz as a denizen of the Gulf weed, on whic'a it is 

 said to walk with legs, and not to swim as other fishes do. 



From the above account I suppose that I must have caught 

 the fish in question in July last, during the homeward voyage of 

 H.M. S. Charybdis, in lat. somewhere about 15° N., and from 

 the Gulf weed, as described by Prof. Agassiz. The preparation I 

 shall be happy to present to the British Museum if it should turn 

 out to be a species of which no specimen exists in 'that institu- 

 tion. 



It will be observed that the pectoral fins are developed into 

 arms, and the ventrals into legs, though less perfect in form than 

 are the arms. 



Sir Pliilip Egerton has seen it, and pronounces it to be a 

 species of blenny, a shallow water fish ; and Capt. Spratt has 

 kindly infnrmed me that it recalls to his mind a theory enter- 

 tained by the late Prof. Forbes, that the Gulf weed is the pro- 

 duct of a shallow water, such as existed before tlie subsidence of 

 the Miocene formation ; and that it may contain a shallow sea 

 fauna, although found in latitudes where the ocean is deepest. 



It is a curious fact if such be the case, and one which would _ 

 appear to have lis counterpart in the deepest holes from which 

 Forbes dredged molluscs, which have continued t > live therein, 

 and to have survived their congeners of former geological epochs. 



J. E. Meryon 



The Law of Variation 



In Mr. A. W. Bennett's notice of the sixth edition of the 

 " Origin of Species," he calls attention to the insufficiency of 

 the theory of " Natural .Selection " to explain original variations, 

 and says, " If it is admitted that impoitant modifications are due 

 to 'spontaneous variability,'" &c. Now is tliere no cause for 

 primary, or spontaneous variability ? 



Is it not presumed under the law of inheritance that, in order 

 that the offspring may be the exact type of the parent form, 

 all the conditions of generation and life, and all the forces that 

 affect life, whether generating or external, must hz precisely the 

 same ? Strictly speaking, under the varying circumstances of life, 

 this is never the case ; hence slight individual variations ; for no 

 individual force can operate as a cause without its effect. Thcs2 

 caused variations may sometimes be wide, and may be helpful 

 or hurtful ; if helpful, "Natural SeJection" would take them 

 up and preserve tliem and improve them. A. J. Warner 



Marietta, Ohio, March 14 



Actinic Power of the Electric Light 



Mr. Meeze says in Nature of the 4th, " May not the great 

 actinic power of the electric light be due in a great measure to 

 the secondary waves produced by the magnitude of the disturb- 

 ing force?" 



This may be true, but there is a cause for the fact which is 

 known to exist, namely, that the electric light is bluer than solar 

 light, that it is to say, it contains a greater proportion of the 

 shorter and more refrangible waves, which have the greatest 

 actinic power. This is due to the absorption of more of the 

 shorter tliaii of the longer waves — in other words, absorption 

 rather at the blue than at the red end of tlie spectrum — which 

 takes placed in the sun's atmosphere. In the magnesium light 

 also, great actinic power is associated with a blue tint. 



Joseph John Murphy 



