Nov. 25, 1880] 



NATURE 



n 



caused by the caloric evolved by the transition of the aqueous 

 vapour of the breatli into the liquid or solid form. 



Before seeing Dr. Roberts's explanation I referred the matter 

 to the greatestliving authority on heat, and he, after carefully 

 repeating my experiments, was of opinion that the heat was 

 produced by the compression of the air when forced through the 

 material. Had he known of Dr. Roberts's simple but ingenious 

 variation of the experiment there Is no doubt he would have 

 accepted Dr. Roberts's explanation. R. E. Dudgeon 



November iS 



The following experiment may serve to supplement the obser- 

 vations of Dr. Roberts as to the cause of the high reading of a 

 thermometer wrapped in a handkerchief and pL-iced in the mouth. 

 An ordinary non -registering thermometer was wrapped in about 

 tn elve folds of a dry linen handkerchief placed iu the mouth, 

 and the following readings taken at intervals of one minute :— 

 Inspiration was effected through the nostrils, expiration through 

 the handkerchief. The thermometer w as in the mouth from the 

 beginning to the end of the experiment. Temperature under the 

 tongue before commencing, yf'o C. The reading of the ther- 

 mometer wrapped as above described, one minute after introduc- 

 tion into the mouth, was 43° 'o. At the end of the second minute, 

 44°-i, 3rd 42°-9, 4th 4i°-2, 5th 39°-6, 6th 3S°-2, 7th 37°-i, Sth 

 36°-9, 9th 36°-9, &c. After the experiment the temperature 

 under the tongue was 37°'6. Capillarity is probably the cliief 

 cause of the rapid condensation of water, and the consequent 

 liberation of heat in the dry fabric. 



In connection w ith the above I may mention a schoolboy's 

 trick, viz., gripping the arm of a schoolfellow with the teeth and 

 breathing forcibly through his coat-sleeve. The sensation of 

 heat thus produced is much greater than ^when the breath is 

 allowed to impinge on the bare skin. 



In conclusion, I must freely confess that Dr. Djidgeon com- 

 pletely upset my objection, as to compression of the bulb having 

 anything to do with the high reading, by the experiments quoted 

 in his last letter. F. J. M. P. 



Coral Reefs and Islands 



In my letter on " Coral Reefs and Islands," published in 

 Nature, vol. xxii. p. 558, 1 have just noticed an important 

 slip in w riting which demands correction. 



In the third paragraph and ninth line, for mclrcs read miles, 

 so that the passage shall read thus : "On the Florida coast we 

 have barriers with channels 10-40 mihs wide." 



More accurately, the space between the southern coast of 

 Florida and the line of Keys (old barrier reef) gradually widens 

 from a few miles in its eastern to more than 40 miles in its 

 western part. The channel between the line of Keys and the 

 present reef is 6-7 miles wide and about 150 miles long. 



Berkeley, California, November 2 Joseph LeConte 



Vox Angelica 



I HAVE received a letter from Mr. Samuel Ray of Stoke 

 Newington with reference to my remarks on the Vox Angelica 

 stop on an Estey American organ. Mr. Ray informs me that 

 Gordon's supplementary tuning-valve is used for the desired 

 effects. The rationale of the method is, that by partly closing 

 the mute the reeds are flattened, just as one reed is when the key 

 is partially depressed. Mr. Ray also says, that by pulling out 

 the stop a little way and making the reeds beat the latter are 

 liable to be drawn out of tune ; but this was the original method, 

 but is now improved upon. A separate mute is placed on the 

 top of the tutes, so that the wind strikes one of the sets of reeds 

 vertically, whereby undue strain is avoided. 



George Ravleigh Vicars 



Woodville House, Rugby, November iS 



Fascination (?) 

 Probably none of your readers have thought it worth while 

 to make any comment on the letters on this subject which have 

 recently appeared, because it would seem needless to discuss the 

 origin of "fascination" by means of the eye of a snake (or 

 whatever may be the stimulus to the alleged condition) while all 

 the evidence we can obtain from these reptiles in confinement 

 proves that the condition does not exist. It devolves upon those 

 who might object to observations on reptiles in a glass case as 



untrustworthy, to show us why — all their other actions being 

 normal — the prisoners should not exhibit the same habit iu 

 respect to this " fascination," as they are alleged to practise 

 when free. It is rather late in the year now ; but if Mr. L. P. 

 Gratacap will take the first opportunity of seeing snakes feed, 

 and if any of your readers will pay a visit to the Zoological 

 Gardens, both he and they will, I think, come to the conclusion 

 that, beyond the expression of a little surprise (on the part of 

 ducks and pigeons chiefly) w^hich soon wears off at the sight of 

 an nnfainiliar object, both the bivds and animals regard the 

 snakes with marked unconcern. I have seen a guinea-pig, after 

 finding no place of exit from the cage, quietly settle itself 

 down in the midst of the coils of an Australian constrictor, 

 shut its eyes and go to sleep. Ten minutes afterwards the snake 

 had moved, and the guinea-pig was washing its face with its 

 paws. Not once, but a dozen times, a rabbit has nibbled the 

 nose of a River Jack viper (V. rhinoceros) in a pretty, inquiring 

 way, heedless of the strong blows the reptile would administer 

 with its snout to the impertinent investigator of that queer- 

 looking object. For fully ten minutes one day a rabbit sat 

 gazing at the poised and threatening head of a puff adder, now 

 and then reaching forward to smell the reptile's nose, and anon 

 sitting on its hind legs to wash its ears, and again returning to 

 the " fascinating " object of its inquiries. If during that time 

 the rabbit had fallen into the state of trance, it was so soon 

 released from that condition as to be able to attend to its own 

 comfort and busy itself about its toilet. The birds show no 

 more recognition than the other animals of the dangerous posi- 

 tion in which they are placed. We see them hopping about on 

 the snakes and pecking lustily at their scales ; sitting on the 

 branches, preening their feathers and behaving themselves just 

 as though no such dreadful (or pleasing?) sensation as "fascina- 

 tion " was possible ! 



I saw once a sparrow perched upon the body of a snake 

 twisted round a branch, and preening itself. By-and-by a 

 constrictor crept up slow ly, touched the bird w ith its nose, and 

 then threw? the crushing folds around it. The deliberate approach 

 of the snake and the unconscious attitude of the sparrow, con- 

 cerned about its private affairs, would have st.aggered any ordi- 

 nary believer in "fascination." I have closely watched the 

 behaviour of snakes intent on feeding. It may be a sudden rush, 

 when the victim has no time to see its enemy, or the gradual, lazy 

 advance of the reptile ; in either case the doomed victim betrays 

 ho suspicion of danger — at least so far as I have been able to 

 ascertain after passing some hundreds of hours contemplating the 

 snakes in the unequalled representative collection of the Zoological 

 Society. 



The expression in Mr. Gratacap's letter, "glittering eyes, 

 applied to the orbits of a snake, which are veiled by the "anto- 

 cular " membrane, and capable of very slight movement, may 

 remind us of Virgil's " Suffecti sanguine et igni," and help to 

 confirm the " basilisk" (not a snake, by-the-by) superstition, but 

 can only serve to perpetuate a myth. Whatever may be the 

 value of Mr. Foot's opinion, I would ask, " Who has ever seen 

 a snake ' raise its tail ' after the manner of the cats ? " 



Charles Darwin has much to say on this subject to any one 

 who chooses to consult the " Origin of Species." He does not 

 see any advantage in the cat's " waving " tail or the noise of the 

 " rattle " of Crolalns, for no predatory animal would derive any 

 benefit from a signal of warning to its prey. The snake certainly 

 never "waves" its tail when intent on mischief. 



Arthur Nicols 



Soaring of Birds 



Referring to Nature, vol. xxiii. p. 10, may I suggest the 

 following?— The question seems to be: "How can birds, 

 havinw attained a certain elevation, thence rise without further 

 muscular effort ? " If I am not in error in what follows, they can 

 theoretically do so if they start with a difference between their 

 horizontal velocity and that of the wind, and en,l with a less 

 difference; e.g., if they start at rest with respect to the earth, 

 and end by drifting with the wind entirely. 



Take this last case, and consider the earth as plane, and the 

 wind as horizontal, and having a velocity = -j with respect to the 

 [earth and] bird. Finally we suppose the bird gains a horizontal 

 momentum = tnv. Then, by conservation of horizontal mo- 

 mentum, the only force t;cting being vertical, the air must lose an 

 equal horizontal momentum. 



Now we know that in all cases of bodies colliding and ulti- 

 mately acquiring the same velocity, while we have conservation 



