Feb. 6, 1890] 



NATURE 



Z^l 



secondary bows formed by light from the real sun reflected from 

 the water after leaving certain drops ; primary and secondary 

 formed by light from the sun reflected at the water, and, after 

 leaving certain other drops, again reflected at the water. I have 

 called the latter four distinct bows, because, although they 

 looked like reflections of a solid set of four arcs, they were really 

 formed by means of drops distinct from those which helped to 

 make the first four bows. I append a sketch of what I saw. 



Percival Frost. 

 15 Fitzwilliam Street, January 29. 



[We have received other letters on the subject of Mr. Scouller's 

 letter.] 



Thought and Breathing. 



I SEND you some extracts from the Sanskrit Yoga-siitras 

 which treat very fully of the prawajama, or the expulsion and 

 retention of breath, as a means of steadying the mind. 



A Yogi has first of all to assume certain postures which help 

 him to fix his mind on certain objects. He cannot concentrate 

 his mind while walking or running. He ought to assume a firm 

 and pleasant position, one requiring little effort. To judge, 

 however, from the description given of some of these postures, 

 they would seem to us anything but pleasant. 



When a Yogi has accustomed himself to his posture, he 

 begins to regulate his breath — that is, he draws in the breath 

 through one nostril, retains it for some time in the chest, and 

 then emits it through the other nostril. The details of this pro- 

 cess are given in the first chapter of the Yoga-siitras, sutra 37. 

 Here the commentator states that the expulsion means the 

 throwing out of the air from the lungs in a fixed quantity through a 

 special effort. Retention is the restraint or stoppage of the motion 

 of breath for a certain limited time. That stoppage is effected by 

 two acts — by filling the lungs with external air, and by retaining 

 therein the inhaled air. Thus the threefold pra«ayama, including 

 the three acts of expiration, inspiration, and retention of breath, 

 fixes the thinking principle to one point of concentration. All 

 the functions of the organs being preceded by that of the breath 

 — there being always a correlation between breath and mind in 

 their respective functions — the breath, when overcome by 

 stopping all the functions of the organs, effects the concentration 

 of the thinking principle to one object. 



Rajendralal Mitra, to whom we owe a very valuable edition 

 of the text and translation of the Yoga-siitras, adds the fol- 

 lowing remarks : — " All other Yogic and Tantric works regard 

 the three acts of expiration, inspiration, and retention performed 

 in specific order to constitute prawayama. The order, however, 

 is not always the same. . . . The mode of reckoning the time 

 to be devoted to each act is regulated in one of two ways : (i) 

 by so many repetitions of the syllable om, or the mystic mantra 

 {formula) of the performer, or the specific mystic syllables (vija) 

 of that mantra ; (2) by turning the thumb and the index-finger 

 of the left hand round the left knee a given number of times. 

 The time devoted to inspiration is the shortest, and to retention 

 the longest. A Vaishwava in his ordinary daily prayer repeats 

 the Vija-mantra once while expiring, 7 times while inspiring, 

 and 20 times while retaining. A Sakta repeats the mantra 16 

 times while inspiring, 64 times while retaining, and 32 times 

 while expiring. These periods are frequently modified." 



The usual mode of performing the prawayama is, after 

 assuming the posture prescribed, to place the ring-finger of the 

 right hand on the left nostril, pressing it so as to close it, and to 

 expire with the right, then to press the right nostril with the 

 thumb, and to inspire through the left nostril, and then to close 

 the two nostrils with the ring finger and the thumb, and to stop 

 all breathing. The order is reversed in the next operation, and 

 in the third act the first form is required. The Ha/Aadipika 

 says:— "By the motion "of the breath, the thinking principle 

 moves ; when that motion is stopped, it becomes motionless, 

 and the Yogi becomes firm as the trunk of a tree ; therefore the 

 wind should be stopped. As long as the breath remains in the 

 body, so long it is called living. Death is the exit of that 

 breath, therefore it should be stopped." 



Some of the minor works on Yoga expatiate on the sanitary 

 and therapeutic advantages of practising prawayama regularly at 

 stated times. In America some spiritualistic doctors prescribe 

 the same practice for curing diseases. 



In India pra«ayama is only a means towards a higher object — 

 namely, the abstraction of the organs from their natural functions. 

 It is a preliminary to Yoga, which consists in d/idraad, stead- 



fastness, dhydna, contemplation, and samddki, meditation, or 

 almost a cataleptic trance. These three are supposed to impart 

 powers or siddhts which seem to us incredible, but which never- 

 theless are attested by the ancient Yogis in a very bond-fide 

 spirit, and deserve examination, if only as instances of human 

 credulity. I say nothing of modern impostures. 

 Oxford, January 22. F. Max Mijller. 



In connection with Prof. Leumann's recent researches into 

 the relation between changes in respiration and changes in 

 certain cerebral functions, it seems curious that the employment 

 of deep and rapid respiration as an ansesthetic has received so 

 little attention. Some dentists order their patients to respire as 

 quickly and fully as they can for a period which varies, I believe, 

 from four to six minutes, although as to the exact duration I 

 am insufficiently informed. At the termination of this period 

 the patient becomes giddy, and to a great extent loses con- 

 sciousness, when a short operation can be painlessly performed. 

 The patient, while unable to move his arms, opens his mouth at 

 the order of the operator. I have heard of no casualties or evil 

 effects from this mode of treatment. W. Clement Ley. 



Chiff-ChafF singing in September. 



During more than forty years' observation of the singing of 

 birds, I have invariably heard the chiff-chaff singing in Sept- 

 ember, although the song is much less frequently repeated than 

 in the spring. In connection with this observation I may men- 

 tion that both the male and female birds appear to be invariably 

 mute for two or three days after their spring arrival in Northern 

 Europe. W, Clement Ley. 



Lutterworth, January 31. 



Foreign Substances attached to Crabs. 



I have read in recent numbers of Nature some letters on 

 sponges attached to crabs. 



There are two crabs on the east coast of Australia — one of 

 them allied to Dromia vulgaris — which cover themselves with 

 sponges or with a composite Ascidian. I have in one case 

 counted no less than seven species of sponges on one individual 

 crab. 



The Ascidian referred to is usually from ten to thirty times as 

 large as the crab to the back of which it is attached. 



Among the specimens brought by me from Australia, and 

 now deposited in the National Collection of the British Mu- 

 seum, there are some of these crabs with sponges and Ascidians 

 attached. 



These might, perhaps, be interesting to your correspondents 

 on the subject. R. V. Lendenfeld. 



University, Innsbruck, January 25. 



Foot-Pounds. 



"A. S. E." will find m ^ments, of resistance, of bending, or of 

 turning, expressed in foot-pounds (often inch-pounds or foot tons) 

 in any treatise on civil, mechanical, or marine engineering, on 

 architecture, land or naval, and, in fact, in every treatise on 

 real mechanics he may consult. Why, then, should a different 

 terminology be adopted in a Civil Service examination paper ? 

 In metric units, moments are given in kilogramme-metres or 

 -centimetres ; but in the C.G.S. system I do not suppose it is 

 suggested to measure moments of dyne-centimetres in ergs. 



February 3. A. G. Greenhill. 



If "A. S. E." will push his researches further, he will find 

 that in Government dockyards the stability moment on ships is 

 calculated in foot-tons. V. 



February 3. 



PROF. WEISMANN'S THEORY OF HEREDITY, 



IN Nature of October 24, 1889 (p. 621), appeared a 

 criticism by Prof. Vines of my essays on heredity 

 and allied subjects. I should be glad to reply briefly to 

 his objections, and the more so as I hope thus to be able 

 to place the scientific problems at issue in a somewhat 



