2^6 



NATURE 



[December 22, 1910 



at South Kensington at my disposal, an investigation was 

 begun, which led to the discovery of recalescence on 

 September 12, 1873. On that date I noticed that accom- 

 panying the Gore effect in cooling iron, and at the same 

 critical temperature, a sudden reheating or a]ter glow 

 occurred. It was more difficult to detect the reverse effect 

 on heating, but a momentary arrest of the heating 

 appeared to occur at the critical temperature. The 

 Chatelier thermo-electric pyrometer was unknown at that 

 time, and I had to have recourse to an air thermometer, 

 which showed that the after glow was not an optical 

 illusion, but a real, though transient, accession of tempera- 

 ture, due to a liberation of latent heat and not to surface 

 oxidation of the iron, as was shown by the recalescence 

 occurring as strongly in an atmosphere of nitrogen or other 

 inert gas as in air. Furthermore, this effect appeared to 

 synchronise with the critical temperature at which iron 

 lost on heating and regained on cooling its magnetic 

 power, and with the remarkable thermo-electric inversion 

 in iron which Prof. Tait had then recently discovered. 

 I noticed, also, that a crepitation occurred in the iron at 

 this temperature resembling the Page effect on magnetising 

 iron. 



These and other observations were described, and the 

 experiments exhibited at the British Association meeting 

 at Bradford a few weeks later, September, 1873, and the 

 paper was published in the Philosophical Magazine for 

 December, 1873.^ An interesting discussion on recalescence 

 followed the reading of my pajier, in which Prof. Clerk 

 Maxwell, Mr. Herbert Spencer, Prof. Carey Foster, and 

 others took part. This was reported in the local papers 

 at the time, and happily is preserved in a number of the 

 now defunct Quarterly Journal of Science.^ 



Later on a British Association Committee was appminted 

 to report on the whole subject. Prof. Geo. Fitzgerald 

 being chairman and myself secretary. Unfortunately, a 

 long delay occurred in the publication of the report, partly 

 owing to my removal to Dublin and the pressure of work 

 in the chair to which I was appointed ; meanwhile, the 

 subject was greatly enriched by the researches of others, 

 especially by M. Osmond, who in 1886 made it the starting 

 point of his classical investigations. An interim report 

 by the British Association Committee was, it is true, pub- 

 lished, but I would specially refer to the final lengthy 

 report published in the Proceedings of the British Associa- 

 tion for 1890, which had the advantage of Prof. Geo. 

 Fitzgerald's cooperation, he having witnessed and 

 corroborated some of the earlier exj>eriments described 

 therein. It is there shown that in 1875 two recalescent 

 points were found, most markedly in steel wire, " the 

 second and far stronger after glow being exactly coincident 

 with the sudden elongation of steel wire during cooling " 

 (the Gore effect). As that report is easily accessible, I 

 will not refer to the other observations it contains. Amid 

 the large literature on this subject which has grown up 

 attention should be directed to an excellent investigation 

 by a Swede, Dr. G. E. Svedalius, on the " Measurement 

 of the Anomalous Changes in the Length and Temperature 

 of Iron and Steel during Recalescence " ; this was com- 

 municated by Prof. Geo. Fitzgerald to the Philosophical 

 Magazine for August, i8q8. 



With regard to the allotropic form of iron which appears 

 to be produced at high temperatuies — Osmund's $ iron — 

 and the liberation of the latent heat of allotropy during 

 cooling causing recalescence, I may point out that Prof. 

 Tait, from his thermoelectric researches, had been led to 

 the conclusion, as stated in his Rede lecture in 1873. 

 " that iron becomes a different metal on being raised 

 above a red heat." But I believe Prof. Geo. Forbes 

 was the first to suggest and pubHsh the fact that recales- 

 cence might be due to the liberation of the latent heat of 



1 " On Certain remarkable Molecular Changes occurring in Iron Wire at 

 a Low T?ed Heat. Phi'l. Mag., December, 1873, p. 472 ; see also my paper 

 in the fnllowine number of the PAzi. Afag: 



2 UpfYi the publication of my pappr in the Phil Mag:, Dr Gore wrote to 

 me as follow-;, in a letter dated Edebaston, December 22, 1873 :—" Your new 

 discoveries re'specin? the molecular changes in iron, described in the P/u'l. 

 Mag. for this month, have greatly pleased me ; especially the sudden deve- 

 lopment of heat attending the elongation during cooHne, and the sudden 

 shortening during heating." Furthermore, when Sir Roberts-Austen in a 

 lecture before the British Association in i^Sg made much the same error as 

 that quoted at the beginning of this note. Dr. Gore at once wrote to me and 

 expressed his great surprise that the discovery of recalescence should be 

 attributed to him. 



an allotropic form of iron. Writing to me upon my experi- 

 ments on April 18, 1874, he remarks : — " It would follow 

 that iron heated to an intense white heat assumes an 

 allotropic form, and that at this temperature [of recales- 

 cence] when cooling it changes to the other form and 

 gives off latent heat." 



In conclusion, let me congratulate Prof. Arnold upon 

 his investigations, extending over so many years, and the 

 light he has thrown on the causes of the different phases 

 of recalescence and the importance of the carbon change 

 point. No doubt he is aware that M. Svedelius, in the 

 paper referred to above, also experimented with electro- 

 lytic iron. Referring to the expansion at the critical 

 temperature, Svedelius says : — " In a rod of electrolytic 

 iron the magnitude of the expansion at D, decreased very 

 rapidly with every renewed heating, and after the fiftieth 

 heating no trace either of the critical point D or D, could 

 be discovered"; and he adds in a footnote: — "This con- 

 firms the statement made long ago by Prof. Barrett that 

 in very pure iron the anomalous contraction and expansion 

 could be ' washed out,' as it were, by repeated heating 

 and cooling." I do not know whether Prof. Arnold has 

 experimented with a very low carbon " burnt iron " to 

 ascertain whether any recalescent points remain in such 

 iron. W. F. Barrett. 



Kingstown, co. Dublin, December. 



Captain Cook Memorial. 



Under the auspices of the British Empire League, a 

 very representative and influential committee has been 

 formed to carry out the proposal made by Sir Joseph 

 Carruthers, K.C.M.G., ex-Premier of New South Wales, 

 that a monument should be erected in London to th^- 

 memory of Captain Cook ; but I venture to ask. is thi- 

 the best way to honour the memory of the illustrious 

 navigator? Captain Cook was a great seaman, geo- 

 grapher, and ethnologist ; indeed, he was one of the fore- 

 most of the men of science of his day. As his life was 

 devoted to discovery of various kinds, surely the best 

 memorial to him would be to establish a fund, associated 

 with his name, the interest of which should be devoted 

 to the prosecution of investigations analogous to thos'- 

 in which he spent his life and met his death. 



Cambridge, December 13. 



A. C. Hadbon. 



Accuracy of Time on Magnetograms. 



I AM greatly interested by Dr. Krogness's letter in 

 Nature of December 8 directing attention to this matter. 

 W'e have been investigating this point for some time by 

 interrupting both trace and base line in our Adie magneto- 

 graphs. 



We find that, in general, if the times are taken from 

 the base line we should actually get declination for about 

 two minutes later, but horizontal force and vertical force 

 for two minutes earlier. The error is probably not con- 

 stant, and so we have decided to interrupt the trace. It 

 may be of interest to say that we have been able to reduce 

 the interruption to one minute, which corresponds to 

 i mm. on the paper. George W. Walker. 



The Observatory, Eskdalemuir, Langholm, 

 Dumfriesshire, December iq. 



The Quadrantid Meteor Shower, 



If the maximum of this meteor shower should occi 

 when the earth is in the same position with regard to tJ 

 sun as was formerly the case, it would take place in til 

 davtime of Januarv 3, 1911, but this shower does not seei 

 to 'have been sufficiently watched of late years to asc^ 

 tain when the maximum now occurs. There is, however 

 some reason to believe that it will not be until the eveij 

 ing of January 3, in which case, as there is no nioonlighl 

 it would be a' very favourable opportunity for its observa 

 tion in this country. -As the maximum is of short durj 

 tion it ought to be more extensively watched for annual 

 than appears usually to be the case. 



T. W. Backhouse. 



West Hendon House, Sunderland, December 13. 



NO. 2147, VOL. 85] 



