March 7, 1895] 



NA TURli 



453 



Ireedoti of Atoms is not inconsistent wiih the various In- 

 urnal Movements exhibiied by the Spectra of Gases." By 

 1 r.if. G. K. Fiizgeraltl, K.K.S. 



U has been generally held that a sulTicient freedom of internal 

 motion in an aiom to explain the spectra of gases pioved that 

 the theorem as to equal partition of energy among all degrees 

 of freedom could not hold, and various siigg'Stions have lieen 

 made as to v\hy the proofs as given by Maxwell, IJolt/.mann, 

 anil others, fails in this caie. Prof Schuster has suggested that 

 the numerous lines need not involve the same number of 

 degrees of freedom, as it is possible that there maybe con- 

 nections between them such thai one or two coordinates would 

 define a mutton which when analysed into us Fouiitr com- 

 ponents, as is dune by a gratini; or prism, would proiluce a 

 very complex system of lines. II twever, even one degree of 

 internal deedom would inter fere very seriously with the observed 

 value of the ratio of specific heats, and the object of this note 

 is to ex| lain how this dilTiculiy may be surmounted without 

 supposing that the iheoiem as to tqual parttion of enerj^y is 

 untrue, f^r it is not by any means disproved because a certain 

 form of proof fails in certain cases. 



It has been long held that the motion of the eleclrons on 

 neighbouring atoms is very much controlled by the ether 

 between them. The wave-lengih of light is geneially many 

 times as great as the molecular distances, so ihat the ethei is a 

 practically rigid connector beiween neighbouring electrons. 

 Suppo e now, as a particular example, that lO'' atoms are in this 

 sense, and so far as the motion of electrons is cc nctrnei', within 

 one another's control. In this case the motion of ihese ic'' 

 electrons might be defined by means of, say, three coordinate^. 

 Hence, if the atoms were spheres, there would be 3 x 10** degrees 

 of freedom plus these three degrees defining ihe motions of all the 

 electrons. Now, if the total energy be equally distiibuted 

 among all these degrees of freedom, each atom will only have 

 its share of the electromolions, and its energy of external 

 motion will only be diminished by 3 x iO"*th part owing to the 

 existence of the internal motion of its electrons. I need hardly 

 say that our methods of calorimetry are by no means sufficiently 

 delicate to detect anything of this kin>l. There might be a 

 thousand such internal degrees of freedom, and yet the ratio of 

 specific heats wouldagree with observation. 



The e is some analogy bt-tween this suggestion and the case 

 of a sphere moving in a liquid. The presence of the liquid, 

 although apparently endowed with an infinite numtier of degrees 

 of freed om, does not really increase the degrees of freedt^in at 

 all, because its motion is entirely defined by the motion of the 

 sphere. In a somewhat similar manner, I would suggest that 

 the presence 1 f the million electrons does not sensibly incrta'-e 

 the degrees of freedom of motion of the tuillion atoms, as all 

 their motions may be defined in terms of the motion of a few 

 of them. That the ether wouM so control ihe motit n-, of 

 electrons seems almost certain liom what we know of the 

 rapidity with which electromagnetic actions are transmitted by 

 it, showing how completely it behaves in respect of them as a 

 system of rigid connections. 



"Note on the Disease of Cabbages and allied Plants 

 known as ' Finger and Toe,' &c." By George Massee, Royal 

 Gardens, Kew. 



The disease known in different parts of Britain as "finger 

 and toe," "clubbing," or "anluny," attacks tumips, rape, 

 cabbages of all varieties, radishes, and, in fact, most culiivaicd 

 plants belonging to the order Cnicijerie. Several common 

 weeds are also attacked, namelv, charlock (Bra^siia iuia- 

 pistnini, Boiss.); garlic-muslatd (A.y'«;^/7«/« alliurii. Scop.) ; 

 Ireacle-muslaid (Ervshinim iluiranllwiJes, Linn.), and shep- 

 herd's puise (Ca/i6'/r'(! liiisa pasliins, D.C ). The last-named 

 is reported from the United Stales by Halsled (New Jersey 

 Agric. Coll. Expt. St;ition ; Bullelin 98, l!i93), and has not 

 been observed to be diseased in Britain, although one of our 

 commonest weeds. '1 he disease is characteriseil by the forma- 

 tion of numerous nrdules on the root, which becomes much 

 distorted and soon decays, forming a slimy, fctlid mass. 



Bcikeley (Gani. Chron., ji. 5CO, 1856) a|ipears to have been 

 the first to invesiigate ihe disease from a scientific standpoint, 

 and alihough he did not succeed in deicimining the true c auc, 

 distinctly states that microscoi ic examination revealed the 

 presence of a factor previously unknown in cimnecrion wiih 

 plant diseases. Furthermore, Berkeley pointtd out that wood 

 ashes were a cure for the ilisease, and .supposed this to be due 

 to the presence of potash salts in the ash. 



NO. 1323, VOL. 51] 



Owing to ihe serious amount of dare age caused by " finger 

 ard toe" to the cabb?ge crtp in Russia, the Goveinment of 

 thst country olTered a tewaid lor the di'coverv of ihe cause of 

 the disease. Wort nin (" Pringsheim's Jahrt'," vol. xi. p. 54S, 

 tabs. xxix.-x>xiv., 1S7S) undeitnok the mvestigaiion, and alier 

 years of patient siudy published an elaborate cccount, proving 

 cleaily that the risease was caused by a minute organism re- 

 lated to the fungi, to which he gave the name Plasiiioiiiophnra 

 brassuiT. 



In 1859, Voelcker (Roy. Agtic. Soc. Jctitii., vol. xx. p. loi, 

 1859) pointed out lhat the disease was inlluenced by the 

 am.untof lince present in the soil. Whi re little or no line 

 existed, as in light and sandy soils, the disease al ouniJed, 

 whereas in scil containing lime the disease was absent. This 

 opinion is corroborated by the same autlor at a later date 

 {Op. iil., series iii. vol. v. p. 321, 1S941. 



A series of experiments have been carried out during four 

 successive years at Kew, and they demonslrate the following 

 points : — 



(1) That in addition to cultivated plants, several common 

 weeds belonging to the oriier Crucifenc are attacked by the 

 PUnmoiiiophora. Hence the neces-ity for preventing the 

 growth o( such weeds in fields and hedge- bar ks. 



(2) That the germs tf di.sease are present in soil that has 

 produced a diseased crop, and retain their vitality for at least 

 two years. 



(3) That the development of Plasmodiophoia is favoured by 

 Ihe pre*ence of acids, and checked by the presence of alkalies, 

 agreeing in this respect »ith the furgi rather than wiih 

 bacteria. 



(4) For the purpose of sterilising infected soil, experiments 

 piove that either a dressing of lime or a manure containing 

 pi tash salts is elTeclivp, the last heir g most valuable, as it not 

 only destroys the germs in the soil but also arrests the disease 

 in seedling plants, and at the same lime supplies one of the 

 ingreditnis necessary for the healthy growth of turnips. 



February 21. — "Iron and Steel at Welding Temperatures." 

 By T. Wrights- .n. 



The object of this paper was to demonstrate that the pheno- 

 menon ol welding in iron is identical wiih lhat of regelalion 

 in ii e. 



The author recapitulated experiments made by him in 1879- 

 ?o, described in the Proceedings of ihe Iron and Steel Institute 

 for those years. These experiments were upon cast iron, 

 and )rov(d that this form of iron possessed the properly of 

 expanding while passing from the liquid to the plastic stale 

 during a small ran^eol temperature, and then con racted to the 

 solid state, and thai the expaision amounted to about 6 per 

 cent, in volume. This property of iron resembles the-imilar 

 property of water in freezing, which, within a range of about 

 4' C., expands about g per cent, of its liquid volume, and then 

 contracts as the c<ioling proceeds. 



This properly of waer was investigated by Prof. James 

 Thomson and by Lord Kelvin. The former showed that from 

 iheoreiical considi rati' ns there was reason to expeci that in the 

 case of a body exhibiting the anomalou-- properly of expanding 

 whin looled and contracting when heated, it shoulil be cooled 

 instead of heated by pressure or impact. Lord Kelvin in- 

 vestigated Ihe problem experimentally as affecting freezing 

 water, and completely demonstrated the truth of his brother's 

 reasoning. 



The experiments made by the author in 1879 and 1S80 

 suggested the vie* that this property of ice was connected with 

 ihc pro| eriy of welding in ipin, bui his was only hy[io helical, 

 as ihe experiments had been made on rasi iron, wh ch piobably, 

 on acci uni of the presence of carbon, does not possess the 

 property of weldirg, Further, it was ni>t piaciicahle to experi- 

 ment with M roughi iron in the same way as with cast iron on ac- 

 count of the difficulty of dealing n iih lhat substance in its liquid 

 form. Prof, l-iolierts-Auste" has, however, given metallurgical 

 research a recording piirometer, anil ibis has enableil the author 

 to resume the invesiigaiion al the Mint, The method adopted 

 was ihe healing of bars in an eh ctrie wehler, and as sron as 

 the junction of the bars was at a weMing temperature, end 

 pre -sure was applied by mechancal power, anil the weld effected. 



Olserval'ons show thai a molecular lowering of temj'crature 

 look place in meriiarely the pressure was appliid to the bar 

 when rn the welding condition 



Tl e fall in iem| etatuie vrried'frrni 57° C. to 19° C, accord- 

 ing to the cireunistances of tempi raiute and pressure. 



