38 



NA TURE 



[November ii, 190J 



such an idea. Mr. Wilson's results showed that ions may 

 beconne the nuclei for condensation, but only when the air 

 is both dust-free and supersaturated four-fold. An infinity 

 of ions in dusty air, or in air supersaturated three-fold, 

 would not cause clouds, and as neither dust-free nor super- 

 saturated air have ever yet been met with in the atmo- 

 sphere, it is difficult to see how electrons from the sun 

 could produce cloudy weather. 



(3) These considerations apply, but with still greater 

 force, to Sir Oliver Lodge's ne-^t sentence : — " Local 

 thunderstorms are also a not unlikely result." This is not 

 the place to go into the controversy over the Wilson- 

 Gerdien theory of thunderstorms, but it ought to be pointed 

 out that very strong reasons have been put forward for 

 doubting that the condensation of water on ions plays any 

 part in thunderstorms. George C. Simpson. 



Meteorological Office, Simla, October 21. 



The Identity of Certain Large Birds on Egyptian Vases. 



In looking to-day for an archajological reference in my 

 fiiend JL Jean Capart's valuable volume on " Primitive 

 Ktt in Egypt " (English edition), I noted that he has 

 determined certain birds, delineated on a series of decorated 

 vases, as ostriches. The vases I refer to are to be found 

 on p. 116, Fig. 88; p. 118, Fig. 91; p. iig, Fig. 92; 

 p. 120, Fig. 93; p. 121, Fig. 94; and p. 123, Fig. 96. I 

 venture to suggest that the birds intended to be repre- 

 sented are not ostriches, but flamingos. The inbent beak, 

 the dorsal body-contour, the horizontal ventral region, and 

 the long, lanky legs, uncovered by feathers in the tibial 

 region as in ostriches, all so characteristic of the flamingo, 

 are delineated with great truthfulness on a large scale on 

 the vase illustrated on p. 123, Fig. 96. The crosier-staff- 

 like head is common to all the drawings I have indicated. 

 .Although the representation of the bird on p. 120, Fig. 93, 

 is rather too small and ill-defined to base much upon, the 

 curvature of the neck is yet more that of a ciconiiform 

 than of a struthious bird. Indeed, on p. 119, Fig. 92, the 

 group of birds at the right-hand corner of the vase is 

 actually in pro.Nimity to water, which would hardly be the 

 case if the artist intended it for one of ostriches ; while 

 on the vase illustrated on p. 121, Fig. 94, the four birds 

 delineated have very characteristic horizontal flamingo tails, 

 especially the individual on the extreme left of the row, in 

 which it is spread. These attitudes are in striking contrast 

 with those of certain other large birds included in the zoo- 

 logical group on the rocks of Upper Egypt, reproduced on 

 p. 204, which must be admitted to represent ostriches, at 

 the first glance, from the attitude of their legs in walking, 

 their plumage contour, and their straight beaks. 



The above suggestion I have made during the past two 

 or three years to several Egyptologists, who have recog- 

 nised its valency ; but as I have seen nowhere this emenda- 

 tion, which I believe it to be, recorded, I think it may 

 be of interest to give it publicity, inasmuch as the ethno- 

 graphical deductions to be drawn from these rude pictures 

 can be correct only if the artist's intention has been 

 accurately interpreted. Henry O. Forbes. 



The Museums, Liverpool, October 31. 



November Meteors. 



The absence; of moonlight during the Leonid epoch of 

 the present year will be favourable for observations of 

 this historic shower. For determining on which of the 

 three dates of November 14, 15, and 16 it mav occur, 

 calculations made by the writer point to the night of 

 November ^ 16 as that of the maximum, when, as was 

 the case on the corresponding night of last vear, the 

 number of meteors radiating from the Sickle' may be 

 found by observers to be considerable. The following are 

 details as to this and also other showers that become 

 due during the remainder of the month of November : — 



Leonid epoch, November 16, Sh. G.M.T. This shower 

 is of the sixteenth order of magnitude, having its principal 

 maximum on November 16, i^h. ; other maxima take place 

 on November 16, loh. and iSh., and November 17, 2ih. 



Epoch November 21, qh. 30m., shower of fourth order 

 of magnitude. The principal maxima occur on November 

 NO. 2089, VOL. 82] 



19, 2ih. 15m., and November 20, i8h. 30m. Two other 

 maxima occur on November 20, 2h. 30m. and 5h. 30m. 



Epoch November 21, I7h. This shower, which is of the 

 fifteenth order of magnitude and immediately follows the 

 former, has its maxima on November 21, 2ih., and 

 November 22, iih. 30m. 



Epoch November 26, ih. 30m. This shower, of third 

 order of magnitude, has two principal maxima, on 

 November 26, i5h., and November 27, 2h. There is 

 another maximum on November 27, 5h. 



Epoch November 29, 2oh. 30m., of third order of magni- 

 tude ; has its principal maximum on November 29, I7h., 

 with an earlier maximum on November 29, 3h. 30m. 



Dublin, November 8. John R. Henry. 



The Absence of a Lunar Atmosphere. 



With reference to Mr. Alexander Johnson's letter on this 

 interesting subject, I should like to point out that the 

 theory of radiation pressure is not applicable to gases. 

 Beyond a certain range of minuteness, the effect of radia- 

 tion pressure on particles diminishes, and the size of a 

 particle on which the repulsive force of light is at a maxi- 

 mum is vastly greater than molecular magnitudes. As 

 this is very important, I quote certain numerical deter- 

 minations given by Prof. Arrhenius (" Worlds in the 

 Making," pp. 97, 98) : — 



(i) Diameter of a totally reflecting sphere which would 

 be in equilibrium near the sun under the opposing forces 

 of gravitation and radiation pressure = 0-0015 mm., the 

 specific gravity of the sphere being the same as water. 



(2) For radiation pressure to be elifective, the diameter 

 of the particle must exceed 03 of the wave-length of 

 the incident radiation. If smaller than this, gravitation 

 piedominates. 



(3) Radiation pressure is at a maximum when the 

 diameter of the particle equals the wave-length of the 

 incident light (e.g. 0-5 y. for the blue-green region about 

 A 5000 A.U.). 



(4) In the case of sunlight, which is not homogeneous, 

 Piof. Arrhenius gives 000016 mm. as the diameter of 

 particles on which the effect is greatest. 



As regards the absence of a lunar atmosphere, it seems 

 that we must fall back on the kinetic theory of gases and 

 attribute it to the gradual escape of the more swiftly 

 moving molecules into the surrounding space. 



Charles W. Raffety. 

 Wynnstay, Woodcote Valley Road, Purley, Surrey, 

 November i. 



Pitchblende as a Remedv. 

 As there is now no longer the least doubt as to important 

 cures being effected by means of radium, the question 

 arises whether crude pitchblende would not also have 

 beneficial effect if applied in the case of minor chronic 

 ailments. Perhaps one of the readers of Nature will be 

 able kindly to give some information on this subject. The 

 very minute proportion of radium in pitchblende need be 

 no real objection. If we substitute, in the case of pitch- 

 blende, grams for milligrams and days of application for 

 so many minutes, a disparity of one million is soon made 

 up, and there may be some action, although perhaps 

 different from that of a pure radium salt. Moreover, we 

 must expect a beneficial influence from minute quantities 

 of radio-active substance if the assumption is to tje finally 

 proved that certain thermal waters owe much of their 

 virtue to such traces. In addition to raw pitchblende, a 

 possible utility of pure (yellow) uranium oxide might also 

 be considered. H. Warth. 



SOUTH AFRICAN ASSOCIATION FOR THE 



ADVANCEMENT OF SCIENCE. 

 'T'HE seventh annual meeting' of the South African 

 ■'- Association for the Advancement of Science 

 opened at Bloemfontein on Monday, September 27, 

 under the presidency of the Governor, Sir Hamilton 

 Goold-.Adams. The advantacfe of Bloemfontein for 

 such a conference, in that it is in the centre of South 

 Africa, was observable in the number of busy men 



