February 6, 1896J 



NATURE 



317 



force exists. We cannot conceive the action at any section to 

 be simply a stress of push or a stress of pull. 



What we know from experiment is that, if the ring be actually 

 cut in two, and a piece of, say, paper be put between the halves, 

 the paper will be squeezed with a stress equal to B^/STr. Also, 

 that a pull of that amount would be required to separate the two 

 halves of the ring. 



This means that when they are separated by paper the half- 

 ring A is pulling the half-ring B towards it, and the paper is 

 pushing the half-ring B in the opposite direction with the same 

 force, namely B^/St per square centimetre of the section. 



Of course we may, if we please, say that when there is no 

 paper interposed, each half-ring is both pulling and pushing the 

 other. If a mechanical analogy is wanted, it might be found by 

 imagining a stiff tubular ring with a stretched india-rubber band 

 inside it. Suppose, further, that when such a ring is cut 

 through at any section the india-rubber band is not cut, but only 

 its stift" envelope. Then if we try to separate the halves, 

 we have to apply a force equal to the pull in the rubber band. 

 And when the halves are allowed to come together with a 

 piece of paper between them, they will squeeze it with the 

 same force. 



y\x. Shelford Bid well and Dr. More have done what is 

 equivalent to asking whether the change of length which a ring 

 undergoes when it is magnetised can be accounted for by what 

 I have here called the pull of the rubber band acting to shorten 

 the stift" tube in which it is stretched, the tube being treated as 

 having the same section and the same modulus of elasticity as 

 the real iron ring has. 



But I see no ground for treating this purely hypothetical strain 

 as a " correction " to be applied, either one way or the other, 

 to the observed changes of length. 



The case illustrated by Dr. Chree (on p. 270) is a special one. 

 He there considers the middle piece of a long magnetised bar, 

 -separated by actual gaps from the end-pieces from which it has 

 been cut. To preserve the gaps, the end-pieces must be held 

 fixed. He shows that under these conditions the middle-piece 

 is in a state of tensile stress. So it is, but only because of the 

 pull which the other pieces apply to it across the gaps. Make 

 the iron continuous by closing up the gaps, and the tensile stress 

 disappears. 



To discuss the sign of the magnetic stress at all in the case of 

 a closed ring, seems much like discussing whether a man sitting 

 in a clothes-basket exerts a pull or a push when he tries to lift 

 It by the handles. J. A. Ewixg. 



Engineering Laboratorj', Cambridge, January 28. 



Dr. Chree's letter in Nature of January 23 corrects 

 an error which it is curious has prevailed so long, and in 

 part forestalls a communication Mr. H. Nagaoka and I had 

 intended to make on the subject of magnetic stress. It might, 

 however, be added that the expression B'/Stt used by Dr. More 

 {Phil. Mag., October 1895), and originally given by Mr. S. 

 Bidwell, for the magnetic stress causing changes of length, is 

 incorrect also on another ground, viz. that this quantity is on 

 Maxwell's theory the magnetic stress m air (where, according to 

 the ordinary convention as to dimensions, B = H) and not in 

 iron, where the expression is necessarily of a different form. 



In conjunction with Mr. Nagaoka, I hope before long to discuss 

 this subject more fully. 



E. Taylor Jones. 



University College of North Wales, Bangor, January 25. 



The Astronomical Theory of a Glacial Period. 



Mr. Culverweli. has pointed out to me that I am in error 

 when I include him among those writers who think that the 

 problem of glacial periods is to be solved by considering only the 

 varying amounts of sun-heat at different epochs. On referring to 

 his paper, which I had not at hand when I wrote, I find that this 

 is the case, and that he is careful to limit his calculations as 

 giving only the variations of temperature due to direct sun-heat. 

 He also discusses, though very briefly and inadequately, the 

 effects due to ttatisference of heat from one area to another. 

 Although willingly making this correction at his request, I am 

 still, after another perusal of his paper, quite unable to see that it 

 NO. I371. VOL. 53] 



finally disposes of CroU's theory, much less of that modification 

 of it which I have myself set forth. 



Alfred R. Wallace. 



The Fall of the Altels Glacier, September n, 1895, 



Je vous adresse aujourd'hui un travail sur I'Avalanche du 

 Glacier de I'Altels, que vient de publier la Commission des 

 Glaciers de la Societe helvetique des Sciences naturelles et qui 

 complete I'interessant article de Miss Maria M. Ogilvie : " The 

 Gemmi Disaster" (Nature, vol. Hi. p. 573), 



Ce travail redige par Mr. Heim n'est pas tout a fait definitif en 

 ce que plusieurs points touchant a I'histoire anterieure du glacier 

 de I'Altels n'ont pu etre resolus encore. II serait important de 

 tirer au clair ces points pour pouvoir determiner avec exactitude 

 les causes de I'avalanche du 11 sept. 1895 5 niais, pour cela, il 

 nous faut des photographies du glacier de I'Altels prises avant 

 I'avalanche et remontant jusqu'a quelques annees en arriere si 

 possible. Apres avoir fait depuis plusieurs mois des recherches 

 peu fructueuses a cet egard je prends la liberte de m'adresser a 

 vous, Messieurs, pour donner quelque publicite a ces lignes. 

 Persuade que beaucoup d'amateurs ont photographic I'Altels 

 de I'W., ou du N.W., je les prie de bien vouloir me communiquer 

 leurs epreuves, en indiquant la date (au moins le mois et I'annee) 

 a laquelle la photographic a ete prise. 



En vous remerciant d'avance de votre obligeance, je vous prie, 

 Messieurs, d'agreer I'assurance de ma consideration distinguee. 

 L£ON Du Pasquier. 

 Secretaire de la Commission des Glaciers. 

 Neuchatel, le 21 Janvier. 



Remarkable Sounds. 



I.v Major Head's "Forest Scenes" (London, 1829, p. 205), 

 I have found the passage already quoted by Mr. C. Tomlinson 

 (p. 78, ante), subjoined with this phrase : " It being, in real 

 fact and without metaphor, the voice of winds imprisoned on the 

 bosom of the deep." In a similar manner, Olaus Magnus de- 

 scribes the similar sounds thus : " Mais es lacs Septentrionaus 

 geles, on oit sous la glace une tempete aussi horrible, a raison 

 des vens enfermes sous la glace, qu'on fait d'un tonnerre prove- 

 nant de la grade epesseur des nues." (" Histoire des pays 

 Septentrionaus," Paris, 1561, fol. 21, b). 



Sebastian Miinster, in his article on Iceland, says : — "Car la 

 glace divissee par loppins et brisee en plusieurs parties 

 tourne a I'entour de ceste isle I'espace de huyt moys, et se 

 froisse de si grande impetuosite contre le rivage, qu'elle rend un 

 son horrible et espouantable, et semble advis que ce soit le 

 gemissement ou brayement d'une voix humaine. Cela fait que 

 les plus idiotz croyet que les ames des hommes sont la tor- 

 mentees de froid." ("La Cosmographie universelle," Basle, 

 1552, P- 105 1.) Against this error Arngrimus lonas writes, but 

 at the same time he admits that "this ice at sometimes by 

 shuffling together maketh monstrous soundings and cracklings, 

 and againe at sometimes with the beating of the water sendeth 

 forth an hoarse kind of murmuring." (Hakluyt, "Principal 

 Navigation," 1599, vol. i. p. 563.) 



If it be taken into consideration that so often in the volcanic 

 craters and thermal springs ^ man found the types of the per- 

 petual Abode of Fire, a suggestion would seem quite reasonable 

 that the so-called "Cold Hells" of the Buddhists 2 and the 

 Tauists-* had been the outcome more or less of such dreary, icy 

 sounds.* Kumagusu Minakata. 



January 31. 



The Antiquity of the Finger-Print Method. 



In my letter on this subject that appeared in Nature (vol. li. 



p. 199, December 27, 1894), I have suggested that the ancient 



Japanese usage on divorce-papers of the finger-marks was 



probably adopted from the Chinese "Laws of Yung-Hwui " 



1 Cf. Hardy, " Manual of Buddhism," second edition, p. 27. I re- 

 member a note in Nature about the Indian confusion of thermal springs 

 with the hell, but at the present moment cannot refer to the number and 

 page. 



- See Beal, " A Catena of Buddhist Scriptures from the Chinese," 1871, 

 p. 36. 



S See " Twan Ching-Shih, Yu-yang Tsah-tsu," Japanese edition, torn. ii. 

 fol. 3, h. 



< Indeed, according to Munster, the Icelanders of old believed that their 

 hells were in both the Hecla and the ice. 



