May 



897] 



NATURE 



31 



tumes et Croyances superstitieuses des Cambodgiens," in 

 Cochiiiihitie Francaise ; Excursions et Heconnaissances, No. 

 16, p. 142, Saigon, 1883). 

 So far the practice of augury from combat of shell-fish appears 

 ) be a peculiarity of the peoples in the Far East. Is there any 

 nstance of the same method described in other parts of the 

 ... ,>rld ? 1 Ku.MAGi:su M i nakata. 



-^lay 3. 



Luminous Phenomena Observed on Mountains. 



On Easter Monday, 19th ult., I was ascending Braeriach by 

 its well-known northern ridge, and, shortly after I had crossed 

 the "snow-line," I witnessed a phenomenon of great beauty, 

 the explanation of which I cannot give. The edge of my plaid, 

 of my gloved hands, of my knickerbockers, &.c„ was bordered 

 by a two inch band of brilliant violet light, at the moment of 

 beginning any movement. The light was not visible around 

 anything at rest, nor did it i>ersist ; but only showed at the 

 moment when rest was changed for movement. 



My attention was directed to this for a very short time only, 

 for heavy snow began to drive in my face, and I had to watch 

 where I was going, as the immediate surroundings included 

 dangerous ground. 



After my return, I found an account of a somewhat similar 

 ajipearance in the Cairngonn Club founial, vol. i. p. 159. I 

 copy the account as there given by Dr. John (iordon, of Aber- 

 deen : — 



" Half-way across the snow-slope, while the sun was some- 

 what obscured, but was still sending a considerable intensity of 

 light, we observed a strange ])henomenon. On the side of our 

 body next the snow-slope there was a nimbus of violet light, 

 which clung to clothes, naked fingers, and the shaft of the ice- 

 axe. So plentiful did it appear in the palm of the hand that it 

 looked at times like a pool of violet ink, and one thought it 

 could be pitched away. On shaking the hand, however, the 

 nimbus clung, and was not to be removed. Occasionally the 

 colour varied, taking on shades of brownish-yellow and blue, 

 but violet was the most marked colour. At another time, in 

 much the same condition of light and snow surroundings, one 

 of the party, who was very proud of the beauty of the silver 

 case of his compass, was disgusted to find that it had a dis- 

 tinctly yellow, pinchbeck look. This light refraction or polarisa- 

 tion [?] was not so evident to some of the party, but the writer 

 has observed it before in similar circumstances and atmospheric 

 conditions." 



I may add that, in my own case, no direct sunlight reached 

 nie, as I was in the lower part of a dense cloud or mist. Some 

 of your readers may offer an explanation of this remarkable and 

 beautiful appearance. C. (1. Cash. 



Edinburgh Academy, May 3. 



The Utility of Specific Characters. 



Under the above heading, in your issue of April i, Mr. J. T. 

 <Julick has an interesting communication, in which he asks 

 whether it is possible to explain right-handedness, the dextral 

 -or sinistral coil of snail-shells, and similar features, as having 

 -any utility to the species of which they are certainly character- 

 istic. Can it be due to natural selection that one snail is dextral, 

 while another is sinistral ? 



It is a curious fact, I think first pointed out by Mr. Call, that 

 in the American freshwater shells of the genus Caiiipeloina, 

 sinistral shells are more ntiineroiis among the young than among 

 the adults. Thus, for example, Mr. H. A. Pilsbry (Nautilus, 

 February 1897, p. 118), states that Miss Jennie E. Letson 

 examined a lot of Campeloma dccisuin for him, with the result 

 that, " out of 681 specimens, mainly adult, but including those 

 from one-fourth grown up, none were sinistral. Out of 410 

 shells of the uterine young, 3 were sinistral, slightly over 073 



A o antagonist clans to support — Minamoto or Taira — doubting the accuracy 



■I' an oracle given by his patron-god to induce him to serve under the White 

 Hanner \i c. the Minamoto clan], caused seven white cocks to combat with 

 seven red ones before the shrine of the same deity. And the result was ih.it 

 the red ones [which represented the Red Banner of the Taira clan] were all 

 defeated by white ones, which impelled him to make up his mind to serve 

 the Minamoto clan " (" Heike Monogatari," tome xi.). 



1 Of aHied modes of divination about the decision of a war, I may instance 

 the New Zealander's practice with sticks, and a Gothic king's experiment 



vith swine (see Lubbock, "Origin of Civilisation," 5th ed., p. 245; and 

 Mary Howitt's Appendix to Ennemoser's " History of Magic, " ed. Bobn, 



A. li. p. 458). 



NO. 1437, VOL. 56] 



per cent." He adds: "Probably all who have collected 

 Campelomas have noticed the greater proportion of sinistral 

 examples among the young shells. This doubtless indicates 

 that the reversed condition is an unfavourable one for matura- 

 tion." 



.So here, at any rate, we have some direct evidence as to 

 selection. I think it will strike any one, that while left-handed- 

 ness might be as good for the race as right-handedness, there is 

 a distinct advantage in uniformity, and that consideration 

 alone may perhaps suffice to explain Mr. (lulick's difficulty. 

 Among plants it may seem less obvious, but where seedlings 

 are crowded, uniformity may save space, just as a number of 

 objects of the same shape can usually be packed into less space 

 than those of diverse shapes. More plants can grow in a 

 window-box where all bend to the light, than would be iwssible 

 if half of them bent one way and half another. 



There also occurs to me a theoretical consideration, perhaps 

 of doubtful value. When a germ has diverse potentialities, so 

 that it is left to germinal or environmental selection to decide 

 which course it shall take in development, there must, appar- 

 ently, be a certain waste of germinal energy. Any disadvantage 

 thus arising is ordinarily much more than counterbalanced by 

 the gain due to the adaptability of the organism, or in social 

 species to the power of specialisation of the individual for 

 social purposes. But it may be that when no such advantage 

 is found, there exists a small disadvantage in deviations, 

 potential or actual, from a common standard.^ 



What we really need, in discussing these matters, is the 

 observation of actual facts. The facts above related as to 

 Campeloma are worth more than any amount of theoretical 

 considerations. T. D. A. Cockerei.l. 



Mesilla, New Mexico, U.S.A., April 21. 



The Motion of an Iron or Steel Ball in a Magnetic Field. 

 In Nature, April 29, a method, reprinted from the Physical 

 Review, is given for illustrating the motion of a particle under 

 the action of a force varying inversely as the square of the 

 distance. I think it ought to be pointed out that the force on a 

 small iron or steel ball, due to a single magnetic pole, is not 

 inversely as the square of the distance. It may be shown with- 

 out difficulty that if the strength of the pole be ti, the suscepti- 

 bility of the iron or steel to magnetisation /c, and v the volume 

 of the ball supposed exceedingly small, then the force towards 

 the pcle is 



_ i . ,, *" - . 'U*^\ 



'" ' ' ' I -h %-itK ' dr\r*) 



Thus, assuming that k is constant during the motion of the ball, 

 which, of course, it is not, the force is inversely as the fifth 

 power of the distance, and the curves given can not be regarded 

 as even approximate representations of planetary orbits, but 

 rather as rough representations of orbits described about a 

 centre of force whose law is the inverse fifth (see " Tait and 

 Steele," p. 151). Alex. Anderson. 



(Queen's College, Galway, May 3. 



THE NEW SOUTH AFRICAN MUSEUM. 



THE new South African Museum is situated at the 

 upper end of the Municipal Gardens, about a quarter 

 of a mile distant from the old building, which will now be 

 entirely occupied by the public libfary. 



The new building consists of two floors, of which the 

 upper one contains the principal exhibition rooms ; the 

 large room, measuring 63 feet by 41^ feet, is devoted 

 to the birds, reptiles, and fishes of South Africa ; and there 

 also is the cast of the skeleton of the restored triassic 

 reptile, Pariasaitrus baitii:, Seeley. It is also hoped that at 

 some future time other casts and originals of some of 

 these remarkable extinct forms may be exhibited, among 

 which we may perhaps find the progenitors of our modern 

 mammals. The corresponding room is devoted to the 

 general collection of vertebrates. .A small room contains 

 the anthropological collection, both South .\frican and 

 general. 



