2A.2 



NATURE 



[October 20, 192 1 



Habits of the Hedgehog. 



In Nature of May 19 last (pp. 375-^76) you ^vere 

 good enough to notice at length my paper on "The 

 Ancient Legend as to the Hedgehog carrying Fruit 

 upon its Spines," published by the Manchester 

 Literary and Philosophical Society (Memoirs, vol. 63, 

 No. 2). That paper was written with a view to 

 elicit further evidence for or against the truth of the 

 legend, and for such I asked definitely. Unfor- 

 tunately, so far no one has communicated such to me. 

 I have, however, just found by accident in Nature 

 Notes for 1904 (vol. 16) two records which I had 

 overlooked, and as both are entirely to the point I 

 desire to direct attention to them. 



In one Mr. F. B. Doveton, of Karsfield, Torquay, 

 well known as a poet and musician, writing (p. 118) 

 to inquire whether or not there was any truth in the 

 old legend, adds : " My gardener declares that he has 

 seen the feat performed in an adjacent orchard." In 

 the other Mr. W. H. Warner, of Fyfield, .Vbingdon, 

 vi-rote (p. 152) : " I well remember, many years ago, 

 meeting with hedgehogs in an Oxfordshire orchard, 

 to the spines of which several apples were- sticking. 

 The apples had adhered to the spines, I had little 

 doubt, when the creatures were rolling under the 

 trees. That the hedgehog climbs the apple-tree and 

 carries off the fruit (as country people say it is in the 

 habit of doing) is, of course, absurd." 



One would like, of course, further details in cor- 

 roboration of both these records, but, unfortunately, 

 such are not forthcoming, the two gentlemen in 

 question being now dead. One can, therefore, only 

 note that there seems no reason whatever to doubt 

 the perfect bona fides of either. One of the records 

 is, it is true, second-hand, but it is contributed by a 

 gentleman of known standing, who clearly was pre- 

 pared to accept the truth of his informant's statement. 

 The other is a perfectly definite first-hand statement 

 by a contributor who was (I have ascertained) likely 

 to be trustworthy as a field observer. 



When writing mv article I omitted to mention the 

 not uninteresting fact that the hedgehog, under its 

 old English name of "urchin," enters into the 

 armorial bearings of several English families, either 

 as a charge or as a crest — in the latter case generally 

 on a "mount." Among these is that of Claxton, 

 which bears as its crest an urchin sable, bezantee. 

 The bezants represented originally, without doubt, 

 apples or other fruit stuck upon its spines. 



London, October 5. Miller Christy. 



The Flight of Thistledown. 



It appears that fully blown thistledown in the sun- 

 shine has a positive lifting power, apart from any 

 general upward current of the air. I shall be glad if 

 any readers of Nature can bring facts to confirm or 

 contradict this statement. 



Experiments that give the best result can be 

 carried out as follows : — Find a thoroughly healthy 

 thistle on which the seed is completely ripe and is 

 in process of being shed. By means of tweezers 

 liberate a tuft of the down, and without in any way 

 injuring the symmetry of the whorl take off the seed 

 and the style, which may be recognised through its 

 darker colour. If the tuft in its uninjured condition 

 is liberated in the sunshine on a level plane, it will 

 be found to soar out of sight like a balloon. 



One explanation may be that the sun in shining 

 on the fine cilia warms them and creates a small local 

 current of warm air. 



I have found that swansdown, which appears to 

 afford a much larger surface for a given weight than 



NO. 2712, VOL. T08] 



thistledown, does not have the same soaring power. 

 I am not sure that the effect is purely thermal ; it 

 may be electrostatic. It is very important that the 

 whorl should be undistorted. 



When the tuft is loaded with a seed it appears to 

 be almost neutral, with perhaps a slight lifting power 

 under the best conditions. The whorl and seed in a 

 slight wind will sometimes be carried for several 

 hundred yards, falling and rising in the air-currents. 

 Taking the weight of the seed at 05 of a milligram, 

 it is easy to calculate how many tufts would be 

 required to raise i ton ! Miles Walker. 



College of Technology, Sackville Street, 

 Manchester, September 29. 



A Method of Improving Visibility of Distant Objects. 



The idea may have been suggested before, but I 

 believe it is not generally known and appreciated how 

 very much the power of distinguishing detail in a dis- 

 tant object, and especially of perceiving it in its 

 natural colours, may be improved by the simple device 

 of fitting a small Nicol's prism in the eye-piece end 

 of the observing telescope. The Nicol serves to cut 

 off a great deal of the blue atmospheric "haze" 

 which usually envelops a distant view, and mostly 

 consists of polarised light. Details which are usually 

 lost in the haze, such as the colour of distant rocks 

 or of the vegetation growing upon them, then stands 

 out in a very striking way. 



It may also be worth mentioning that the visibility 

 of the horizon at sea, especially in a haze, may often 

 be wonderfully improved by a similar device. In 

 this case the result is due in part to a suppression of 

 the reflection from the surface of the water as seen 

 through the Nicol's prism. 



It is hoped that these observations will not be 

 merely a scientific curiosity, but may find a practical 

 application. C. V. Raman. 



S.S. Narkuuda, near Aden, September 18. 



Gold-coloured Teeth of Sheep. 



In Nature of June 9 last (p. 459), recently arrived 

 here, is a communication from Mr. W. J. Lewis 

 Abbott concerning the metallic-looking encrustation 

 occurring on the teeth of sheep. In Proc. Linnean 

 Soc. N.S. Wales (vol. 45, 1920, p. 324), abstracted in 

 Nature of April 21 last (p. 249) and reprinted in full in 

 the Chemical News (vol. 122, p. 49), I give a detailed 

 report, with analyses, of this and similar de- 

 posits on the teeth of a number of other animals, 

 including man. In no case is the deposit of a 

 metallic nature, but consists entirely of a salivary 

 encrustation composed usually mainly of phosphate 

 of lime with organic matter. The metallic appear- 

 ance is an optical effect due to the refraction of light 

 by the overlapping thin lammellae of the deposit. 



' I should be interested in examining Mr. Abbott's 

 specimen if he will send me one, and reporting the 

 result in Nature. Thos. Steel. 



Stephens Street, Pennant Hills, New South 

 Wales, August 11. 



The Constitution of Molecules. 



The remarks attributed . to me in Nature of 

 October 13 (p. 219) give an incorrect impression of 

 what I intended to convey to the meeting. The state- 

 ment that the molecular heats " are inconsistent with 

 the arrangement which has been adopted to account 

 for chemical valencv " was not made. 



J. R. Partington. 



October 14. 





