May 16, 1889] 



NATURE 



55 



covering the lower part of the tibial muscles. This adhesion of 

 the yolk-sac to the leg had apparently taken place after the full 

 development of the limb ; and the yolk-sac, in the course of its 

 w ilhdrawal into the cavity of the abdomen, had apparently 

 drawn the foot in with it. The withdrawal of the yolk-sac is 

 generally held to be brought about by the absorption of its con- 

 tents ; if the above explanation of the existing condition be 

 correct, a considerable force must be exerted by this act of 

 absorption if it is capable of dragging the foot, from its normal 

 position, into the cavity of the abdomen. 



E. Waymouth Reid. 

 .St. Mary's Hospital, W., May 6. 



Atmospheric Electricity. 



I SEND you the following account of a curious, and, I believe, 

 rare electrical phenomenon witnessed last week by a friend of 

 mine and myself. 



We had, in the course of a long mountain ramble, reached the 

 summit of Elidyr Fawr (3033 feet), a mountain lying to the north- 

 east of Llanberis, and about four miles north of Snowdon. Being 

 a short distance in front of my friend, I sat down and rested with 

 my back to the cairn, sheltering myself from a cold south wind 

 which was blowing with considerable velocity. In about two 

 minutes I heard a curious buzzing sound commence, apparently 

 proceeding from the top of the post set up not long ago by the 

 Ordnance surveyors. I had heard the same noise about three 

 years ago while descending the areU of the Weisshorn, and 

 on that occasion, as on this, there was a south wind blowing, 

 accompanied by snow — on the Weisshorn in large flakes, on 

 Elidyr Fawr in fine powdery flakes. On the Weisshorn, for 

 above an hour every rock seemed to emit the peculiar buzzing 

 noise, and our ice-axes did the same. We were in too great a 

 hurry, however, to pay much attention to the phenomenon. A 

 day or two after, I related my experience to a gentleman, Mr. 

 Powell — who, I tnist, will forgive me for mentioning his name — 

 and learned from him that he had had a similar experience on 

 the Unter-Gabelhorn, near Zermatt. The day was on that 

 occasion, if I remember right, clear, when the noise was heard, 

 followed in a short time by a flash, and a shout from two of the 

 party that they were struck. No harm was done by the shock, 

 but the sensation was described as being like that which would 

 be felt if every hair of the head were caught hold of and 

 violently twisted. Having heard the sound before, I readily 

 recognized it on Elidyr Fawr, and resolved if possible to study 

 the phenomenon more closely. I first climbed on to the cairn, 

 and found that the sound proceeded from the whole surface of 

 the wood for about two feet from the top of the post. I then 

 raised my stick, which had an iron point, and found that the 

 sound began to proceed from it directly a height of about six 

 feet from the ground was reached. I then put my hand on the 

 part emitting the sound, but could feel nothing. On putting my 

 stick down, and keeping my hand up, the sound proceeded from 

 my hand — from more or less of it according as I raised it higher 

 or lower — and I imagined that on the back of my hand the 

 sensation of being very slightly pricked in many places was 

 perceptible. My friend was much impressed by the peculiarity 

 and intensity of the sound, and agreed with me that it would 

 not be wise to stay long. As_we proceeded along the ridge, 

 after a slight drop, we rose again, and while standing on some 

 rocks, the noise began in our caps, accompanied by such an 

 agitation of the hair that it quite seemed as if we had literally a 

 " bee in the bonnet." There was no sound of thunder, and in 

 the course of about half an hour the srow-storm passed away, 

 not however before we had descended far below the enchanted 

 summit. C. A. C. liowLKEK. 



Halo of the Moon and Formation of Peculiarly Shaped 

 Clouds at Oxford. 



I NOTICED the following very beautiful phenomenon on the 

 night following May 8, aid it seems to me worth recording. At 

 9.45 p.m. the moon was surrounded by a very large halo, tlie sky 

 being quite clear in the immediate vicinity of the same, with the 

 exception of a small accumulation of clouds at the lower part of 

 the halo (to the left of the spectator). 



At 10,45 '^s h^'o ^^^ completely disappeared, and a large 

 cloud was obscuring it and the moon. The margin of the 

 cloud was split up into tongue-like protuberances. At U.20 



the halo had again appeared, but it was not so bright ; the moon 

 was hidden from the spectator by some clouds. 



At 1 1. 30 the clouds had disappeared, and the moon was shining 

 out brightly, but the halo was only very slightly visible, and that 

 only at its highest point. Just before it began to disappear 

 gradually, some of the clouds with the peculiar tongue-like pro- 

 tuberances already mentioned were formed, but they disappeared 

 again after a few minutes. As was to be expected, we had 

 rain on the following day, and some already during the same 

 night. 



I need only just mention that the halo is supposed to be pro- 

 duced by the refraction of light by crystals of ice. Brewster 

 proved this by viewing the sun through some plate-glass on 

 which he had allowed some alum to crystallize out in a thin 

 sheet, when he saw a number of rings closely resembling halos. 



Otto V. Darbishire. 



Balliol College, Oxford. 



Spherical Eggs. 



The problem of packing the greatest number of equal spheres 

 into a given space, to which Prof. Aldis has drawn attention in 

 your columns, is the simplest case of a more general problem 

 which I have employed in my theory of crystallization (Cam. 

 Phil. Trans., vol. xiv. part 3) — that is, the packing of the 

 greatest number of equal and similar ellipsoids into a given space. 

 The solution is that the ellipsoids should be arranged in a manner 

 similar to that described for spheres by Profs. Aldis and Green - 

 hill, so that every ellipsoid be touched by twelve others, and, 

 further, that all the ellipsoids be similarly situated. The curious 

 result comes out that so long as the ellipsoids are all similarly 

 situated the orientation of the axes makes no difference in the 

 number of them per unit volume. They may be turned about, 

 provided they are all similarly turned, without affecting the ratio 

 between the space filled by them and the unfilled space between 

 them. 



In the case of spheres, if tangent planes be drawn through 

 all the points where the spheres touch one another, they will cut 

 up space into regular rhombic dodecahedrons, every sphere being 

 circumscribedby such a dodecahedron. Now, of plane-faced figures 

 which can be described about a sphere and which will exactly 

 fill space, the smallest in volume is the rhombic dodecahedron ; 

 hence the spheres arranged in the way described occupy the 

 minimum volume. In like manner if tangent planes be drawn 

 through all the points where the ellipsoids touch one another, they 

 will divide space into dodecahedrons with quadrilate>-al faces, 

 which will be unsymmetrical, but will be all similar and equal. 

 If the ellipsoids be all turned in a similar manner the dodeca- 

 hedrons will alter in form but not in volume. These dodeca- 

 hedrons are the smallest which can be described about the 

 ellipsoids consistently with the condition that they shall exactly 

 fill space. The condition of similarity in the situation of the 

 ellipsoids involves the consequence that, if we consider one 

 ellipsoid and the twelve others which touch it, four planes can 

 be drawn each passing through the centres of seven ellipsoids. 

 The points of contact of the ellipsoids will lie in those planes, 

 and the tangent planes through these points will be parallel to 

 the diameters conjugate to those planes. Other geometrical 

 properties follow which do not concern the present problem. 



Cambridge, May 10. G. D. Liveing. 



Columnar Structure in Ice. 



There are several notices in existence on the subject of the 

 columnar structure of ice, to which attention has been called by 

 Mr. La Touche (Nature, May 9, p. 35). For instance, a 

 letter by myself in ihe first volume of Nature (p. 481), which 

 contains references to sundry cases of the occurrence of the 

 structure in Britain .ind in other parts of Europe, and offers a 

 suggestion as to the cause. The structure may often be seen, 

 if looked for, and is be t exhibited when a very gradual thaw 

 follows a hard frost. T. G. Bonney. 



SCARLET FEVER AND COIV DISEASE. 



FEW questions have within recent years more en- 

 grossed the attention of the veterinary and medical 

 professions of this country, and have been the subject of 

 greater or more acute controversy, than the relation of 



