August 30, 1906] 



NA TURE 



455 



rays emitted. An experiment vvliicli Dr. Rubens sliowed 

 (o tiic section is of great importance in connection witli 

 tlie interpretation of the piienomena. Light from an electric 

 Janlern is focused upon a cold Welsbach mantle, and after 

 rcllfclion therefrom is re-focused upon a while screen. A 

 bkie cell is interposed to isolate the blue portion of the 

 radiation. If now the Welsbach burner be itself lighted 

 so as to heat the mantle, the image on the screen grows 

 fainter ; the mantle is a poorer reflector for blue light at 

 high than at low temperatures, and it is therefore a better 

 radiator when hot. Indeed, a temperature can be found 

 at which it emits as much blue light as a perfectly black 

 body. When the experiment is made with red light the 

 reflected light increases with the temperature. Thus the 

 fact that a Welsbach mantle is white when cold tells one 

 nothing as to the character of radiation it will emit when 

 hot. In the open discussion which followed Prof. S. P. 

 Thompson considered that Dr. Rubens had demolished 

 statements made by Mr. Swinburne in a previous paper. 

 Prof, Callendar put in a word on behalf of Mr. Swinburne, 

 whom he considered to be essentially in the right, though 

 hi.' had probably not laid sufficient stress upon the import- 

 ance of the selective character of the radiation of ceria. 

 Dr. Rubens e.xpressed himself also as sharing Mr. Swin- 

 burne's views. Sir Wm. Ramsay directed attention to 

 Urbain's recent work on phosphorescence, while the re- 

 corder of the section emphasised the distinction between 

 the opposing schools by pointing out that, according to the 

 " temperature " school, the radiation of the mantle is the 

 sum of the radiations which would be given out by the 

 thoria and ceria if separated and still at the same tempera- 

 ture, while according to the " chemical " school there is 

 present an additional radiation arising from interaction 

 between the constituents of the mantle. Dr. Rubens did 

 not seem willing to admit that the radiation is wholly of 

 this additive type, although it is so in the main. The 

 discussion was enlivened by the president reading replies 

 which Mr. Swinburne had sent ready for use against 

 those with whom he had previously engaged in controversy. 



We will now turn to the papers in connection with 

 which no discussion had been organised. 



Mr. W. G. Duffield read a paper on photographs of the 

 arc spectrum of iron under high pressures. The apparatus 

 by which the pressures were obtained was designed with 

 the help of Mr. Petave!. The photographs which were 

 shown demonstrated clearly that several lines not merely 

 widen out, but undergo an actual shift towards the red. 



Major E. H. Hills and Prof. J. Larmor communi- 

 cated a paper on the irregular motions of the earth's 

 pole, being a preliminary graphical analysis of their causes. 

 In the ensuing discussion Mr. R. D. Oldham asserted 

 that the amount of matter transferred in a recent Indian 

 earthquake was at least 10,000 times that assumed by 

 the authors. Prof. Schuster was inclined to question the 

 accuracy of the observations themselves owing to their 

 minuteness ; the whole shift of axis under discussion 

 amounts only to about 20 feet. Besides, the yielding of 

 the earth owing to the shift of its axis might be the 

 determining cause producing the earthquake, and not vice 

 versS. 



Prof. H. H. Turner read a note on a possible effect 

 of vibration on zenith distance observations, with special 

 reference to the tremors which threaten the Roval Observ- 

 atory at Greenwich. The special effect referred to is 

 similar to one observed long ago in Ireland due to the 

 Ulster railway. If the telescope is set and a train passes 

 the adjustment is found afterwards to be upset. The 

 tremor of the passing train causes a release of any exist- 

 ing strain. Even if at each passage the release of strain 

 may not produce a visible effect, yet the continued action 

 of tremors will be to produce a gradual settling down of 

 the instrument at a different rate from that at which it 

 would proceed if tremors were absent. In the discussion 

 the Astronomer Royal for Scotland declared that in his 

 observatory they were probably free from any tremors, 

 except those caused by their own lathes. The following 

 papers on cosmical physics were also read : — the Astronomer 

 Royal for Scotland, spectroscopic observations of solar 

 eclipses ; Prof. Schuster and Prof. H. H. Turner, a note 

 on rainfall ; the Rev. A. L. Cortie, the connection between 



NO. 1922, VOL. 74] 



disturbed areas of the solar surface and the solar corona ; 

 Miss C. O. Stevens, felescopic observations of meteor- 

 ological phenomena ; the Right Hon. the Earl of Rosse, 

 the measurement of lunar radiation ; Mr. J. E. Clark, the 

 Vork rainfall and sun-spots; and Dr. W. J. S. Lockyer, 

 some barometric and rainfall changes of an oscillatory 

 nature. 



In the department of general physics, Mr. C. E. S. 

 Phillips described a glass of low electrical resistivity con- 

 sisting of thirty-two parts of sodium silicate to eight parts 

 calcined borax, to which 125 parts Powell's flint glass 

 is added in order to increase the stability. This glass is 

 intended to be used for the windows of electrostatic instru- 

 ments which require to be electrically shielded. Its elec- 

 trical conductivity is about 500 times that of the most 

 conducting glass hitherto made. When powdered and 

 fused on to clean copper, it adheres well without cr.acking. 

 The change of resistivity with heat is being examined. 

 In the discussion Mr. Rosenhain mentioned that glasses 

 of the general composition of this one were not unknown in 

 the trade. Dr. Erich Ladenburg gave an account of his 

 researches on nearly pure gaseous ozone. This has a dark 

 blue colour in a thickness of 30 cm. In the absorption 

 spectrum were discovered five new bands which do not 

 belong to ozone, but which always appear when the liquid 

 ozone is allowed to vaporise. The gas to which they 

 belong can be separated from ozone. The change of 

 volume which occurs when the new gas is transformed 

 and the value of the density indicate that the new gas is 

 a more complex form of oxygen. In the discussion Dr. 

 Rubens, in whose laboratory the research had been con- 

 ducted, expressed his belief that it consists of hexatomic 

 oxygen. Mr. Herbert Stansfield showed a series of photo- 

 graphs of thin liquid films in which the two kinds of grey 

 and the three kinds of black are sharply distinguishable 

 from one another. A paper by the Rev. B. J. Whiteside 

 was communicated and read by Prof. F. T. Trouton, 

 the subject being the rate of decay of the phosphor- 

 escence of Balmain's paint. The photometer employed 

 depended upon the inverse square law. The standard light 

 which was emitted through a small hole could be moved 

 to various distances from an opalescent screen placed 

 adjacent to the surface of luminous paint in a box. The 

 distance was adjusted so as to maintain the intensity of 

 the two illuminations the same, and the times correspond- 

 ing to equal shifts of the standard were recorded on 

 a revolving drum. The law of variation of intensity was 

 found to be capable of representation by the formula 

 1 = i/(a-|-6f), where ( is the time reckoned from that at 

 which the paint ceased to be exposed to the exciting light. 

 This result is of great interest, inasmuch as the same law 

 arises in connection with the recovery of overstressed 

 bodies, and this correspondence suggests that the mechanism 

 involved may be similar in the two cases. 



Sir Wm. Ramsay and Dr. J. F. Spencer described 

 experiments on the chemical and electrical changes in- 

 duced by ultra-violet light. These were in some cases 

 confirmatorv of what had previously been done in connec- 

 tion with this interesting subject. The result of greatest 

 novelty and importance is that the fatigue of the surfaces 

 was found to vary in a peculiar way. The rate of falling 

 off when plotted against the time yields a curve presenting 

 obvious breaks. In the case of dyad metals there are 

 two of these breaks, and two places of constant rate of 

 tiring ; for tetrad metals four of these statres are observed. 

 The paper was read bv Dr. Spencer, and Sir Wm. Ramsay 

 followed with an extended statement showing how the 

 electronic theory of matter accounts for the photoelectric 

 effects observed. Dr. O. W. Richardson mentioned that 

 Dr. Smolochowski in some unpublished experiments had 

 succeeded in showing that in a high vacuum the decay 

 phenomena cease to take place. 



An important paper was contributed bv Mr. F. Soddy 

 on the positive charge carried bv the alohn narticle of 

 radium C. The substance of this paner has already 

 appeared in the form of a letter in Nati-re for August 2. 

 Is or is not the aloha particle charged when it commences 

 its separate existence? Mr. Soddv thinks he has nroved 

 that it is not so charged, and, assuming the v.^l'dity of 

 this conclusion, he considers that possibly too much stress 



