56 



NATO RE 



[AW. 1 8, iS8o 



Had the breath been hotter than the mouth the instrument could 

 not have failed to register a higher temperature than 98'4°, but 

 beiiijj really cooler, the instrument, of course, recorded a lower 

 temperature. 



What is then the true explanation of the phenomenon observed 

 by Dr. Dudgeon ? I helieve that it is simply an example of the 

 conversion of latent into sensible heat by th rapid condensadon of 

 aqueous vapour. The organic fabrics which compose our clothing 

 are all more or less hydroscopic — that is to say, they have the 

 capacity of imbibin;^ aqueous vapour and condensing it into the 

 solid and liquid form-:. The expired breath is heavily charged 

 with aquebus vapour ; and aqueous vapour, at the moment of 

 CDndeasation, liberates an enormous amount of latent heat, which 

 thus becomes sensible to the thermometer. In this particular 

 watery vapour exceeds far away all other gases. 



The following experiments were made with a view of testing 

 the correctness of this view. Two strips of flannel were prepared, 

 each six inches long and an inch and a quarter wide. The first 

 strip was rolled, without any prehminary preparation, round the 

 bulb of a clinical therniometer. The bulb, thus enveloped, was 

 iuserted betv\een the closed lips, and the expired air was forced 

 through the porous material for a period of five minutes. The 

 thermometer rose to 104°. The instrument was then allowed to 

 cool, and, after having been re-set, was again inserted between 

 the lips, and breathed through for a second period of five minutes. 

 This time the temperature only ro:;e to loi^. The experiment 

 was repeated a third time for a similar period, but this time the 

 thermometer did not rise above 98'6. 



These results tallied exactly with the requirements of the con- 

 densation hypothesis. During the first period the fresh dry 

 flannel absorbed and condensed the watery vapour passing through 

 it with such rapidity tliat the liberated sensible heat was sufficient 

 to raise the mercury several degrees above the temperature 01 the 

 mouth. In the second period of five minutes the hygroscopic 

 activity of the flannel had been greatly reduced by the previous 

 absorption of aqueous vapour, and the thermometer only ro-e 

 slightly. In the third period saturation had been approached, 

 and the breath passed through the flannel almost without 

 depositing any of its moisture, and accordingly the thermometer 

 only indicated a temperature slightly higher than that of the 

 mouth. 



The second strip of flannel was subjected to a little pre- 

 liminary preparation. In order to increase its hygroscopic 

 activity it was thorou.;hly dried (superexsiccated) by holding it 

 for a few minutes before the fire. When it had cooled down to 

 the temperature of the room it was wrapped round the bulb of 

 the thermome er, and the experiment was proceeded with as 

 before. The re-ult surprised me. In one minute \h& mercury 

 had risen not only to the top of the scale (112° F.), but had 

 filled the little bulb above it, that is to say, it had risen to at 

 least US'" F. When the instrument had cooled it was reset, and 

 inserted again between tlie lips and breathed through for three 

 minutes. At the end of this time the scale marked io5° F. 

 After the instrument had been cooled and reset the experiment 

 was repeated a third time, and the temperature only reached 

 102° after breathing through the envelope for four minutes. A 

 fourth trial of four minutes only produced a record of 9S'4°. 

 Here again the development of heat steadily declined as the 

 flannel became less hygroscopic. 



It is probaljle that, with the superexsiccated flannel the first 

 portions of aqueous vapour condensed at the beginning of the 

 experiment pass at once from the gaseous into the solid form, 

 and constitute that portion of water which is incorporated in 

 intimate union with all organic tissues. This accounts for the 

 extreme rapidity of the development of heat at the commence- 

 ment of the experiment. I found that even a single long 

 expiration through the freshly-warmed flannel raised the mercury 

 to 110° F. 



Dr. Dudgeon's observation will not necessitate a revision of 

 our conclusions respecting the temperature of the breath, but he 

 has supplied us with an exceedingly elegant and easy way of 

 demonstrating the liberation of sensible heat which takes place 

 during the p.assage of water from the gaseous into the solid and 

 liquid ^tate. Wm. Roberts 



Manchester, November 10 



Height of the Aurora 



In Nature, vol. xxii. p. 291, is inserted a letter of Mr. T. 

 Rand Capron, on the determination of the height of aurorcc. 



wherein I read : "It ii unfortunate that simultaneous observa- 

 tions of the .auroral corona are almost entirely wanting. I . . . 

 would be glad if any particulars could now be furnished me." 



Having treated the subject of the auror.x- and their properties 

 in an ample manner in my "Theorie cosmique de I'Aurore 

 polaire " (Alemoric della Societa degli Spettroscopisti Italian!, 

 187S, vol. vii.), wherein I have adduced proofs of the thesis that 

 The corona is an optical illusion, due to the laius of celestial per- 

 spjctize, I was astonished to find the alleged words used by so 

 great an authority. That "simultaneous observations" of the 

 auroral corona will be ever without any result, as far as its height 

 above the earth is concerned, follows already from the known 

 property, that the corona always shows itself in the direction of 

 the local magnetic total force (given by the inclination needle). 



Regretting that such a well-established fact seems not generally 

 known, I take the liberty to refer Mr. Rand Capron to the chapter 

 of my treatise, "Dans quelle Region de I'Atmosphere terrestre se 

 trouveutles R.iyons de I'Aurore polaire, et est-ce que la Couronne 

 est une Chose reelle ? " and will repeat here that very beautiful 

 determinations of the height of streamers and beams were obtained 

 by Prof. Ileis and Dr. Flbgel, and by Prof. Galle in Germany, 

 showing a height of the phenomenon from 20 to 100 miles (of 

 15 in I degree). These results are published in the Zeitschrift 

 der oesterr. Gesellsch.f. Meteor, vii. p. 73. 



I regret to have found no earlier opportunity of answering the 

 request of Mr. Rand Capron, but think that this letter may 

 still have some interest, notwithstanding the valuable article by 

 Mr. Plummer in NATURE, vol. xxii. p. 362. 



Groningen (Netherlands), H. T. H. Groneman 



November 10 



Fascination 



As a contribution to this subject, at least of new material if 

 of no decisive evidence in support of any existing theory, I offer 

 the conclusions which Malachi Foot, Member of the College of 

 Physicians and Surgeons, N.Y., reached in 1S07 relative to this 

 matter. A short memoir of his which I recently met was pub- 

 lished in the Medical Ripository for that year, entitled "An 

 Examination of Dr. Hugh Williamson's Memoir on Fascination, 

 to which is subjoined a New Theory of that Phenomenon," and 

 is striking both in matter and conception. 



The author, after displaying some temper over Dr. William- 

 son's willingne.-s to attribute the well-accredited effects of snake- 

 charming to terror, producing in the victim a condition which 

 he (Dr. Williamson) terms "dementation," and "wherein ex- 

 treme fear stupefies the mind and deprives him of the under- 

 standing," produces his own explanation. Although he acknow- 

 ledges the paralysing effects of fright, and instances quadrupeds 

 ruling lifeless from the effect of fear, deer stricken motionless 

 by the lii,ht of a torch, &c., yet he inveighs against the false 

 reasoning which discovers in thee cases of arrested volition any 

 analogy to the phenomena of so-called fascination. Our author, 

 evidently of no superstitious habit, distinctly admits the fact 

 that the snake repeatedly captures prey by a method seemingly 

 so occult as to merit the ch.aracterisation of fascination, and 

 develops his theory in the light of that very thought. 



He ascribes to the primary sensations of animals, in them 

 unmodified by reflection as to their source or character, complete 

 efficacy to awaken emotions of pleasure of an intensity to us 

 qnite incommensurate with the app.arent causes which evoked 

 them — emotions so powerful as to absorb all other secondary 

 feeling, enfolding the animal in a delightful but numbing trance, 

 whose stages advance from attention through ecstasy to anaes- 

 thesia. And he finds in the eye a sensory centre which most 

 expansively responds to all outward stimuli. This much pre- 

 mised, he applies it to the case in hand. The snake, fixing its 

 glittering eyes with hungry expectancy upon its victim, at the 

 same tiuTe throws its body into graceful curves and raises its tail, 

 undulating with a soft and inviting motion. (Foot insists upon 

 the almost invariable accompaniment of motion as auxiliary in 

 attracting and pleasing the prey.) The bird's eye, once caught, 

 becomes ensnared in the endless succession of contortions, and it 

 draws near, dominated by simple delight. 



As Foot expresses it, "the pleasurable movements of the 

 organs of vision stimulate to approach and excite an eager desire 

 to embrace." Reverie oculorum ensues, and the bird flutters 

 helpless to the ground. Foot speaks of having seen a cat 

 succeed in similarly charming birds by wreathing the body and 

 v/aviug the tail. He might have confounded this with the 



