January 30, 1902] 



NATURE 



!99 



Taking T = 2ii days from the outburst to the date of the 

 photograph taken on September 20 and the angular distance p 

 of the point (a) on Ritchey's photograph as equal to 480", the 

 distance D is equal to 24S light years. The same point on the 

 photograph of November 13 leads to = 265. T^^ difference 

 between these two values of D is, I believe, as Prof. Kapteyn 

 also points out, due to the fact that the plane of the nebula is 

 not normal to the line of sight. Ritchey also points out that, 

 besides the radial expansion, there has been an apparent motion 

 of the nebula round the Nova in position angle. From an 

 examination of the photographs, the nebula seems to be evi- 

 dently a spiral, and the observed shift in position angle would 

 be caused by the gradual illumination of these spiral wreaths by 

 the advancing spherical wave of light. 



It can be shown that, if the sun were removed to the distance 

 of the Nova, it would only be of the io'24 magnitude, so that, 

 even at the present moment, the Nova is more brilliant than 

 the sun. When the Nova was at its greatest brilliancy it was 

 about o '2 magnitude. It must then have been 10,380 times 

 brighter than the sun. If we take the light of the Nova at the 

 earth as equal to a first-magnitude star and take Ziillner's esti- 

 mate of this compared to the sun as ^, then the outer 



5 X lo'" 

 margin of the nebula with a radius of 8' would be 430 times 

 nearer the Nova than the earth, and would receive per unit 



area 430- times the amount of light, or - — rr,, which is equal 

 5 X 10'" 



to , of sunlight. This is about equal to 2 2 times the light 



270500 . 



of full moon. Of course, these figures are of very uncertain value 

 and we must not place too much reliance on them, but if we take 

 the above value of 2'2 times moonlight as that received by the 

 nebula, it at first seems too faint to be visible as reflected light. 

 We must, however, recollect that the light reflected from the 

 nebula at its brightest points cannot have an intrinsic brilliancy 

 of more than an eighteenth-magnitude star, whereas the Nova was 

 of the first magnitude. Hence it is only necessary for the nebula 



to reflect light of an intrinsic brilliancy equal to th 



6,310,000 

 that of the Nova to seem as bright as it actually is, even assum- 

 ing that the nebula has no inherent light of its own. The above 

 figures will evidently require some alterations when the photo- 

 graphs available are carefully measured. W. E. Wilson. 

 Daramona, co. Westmeath, Ireland. 



A Luminous Centipede. 



In your issue of January 9 (p. 223), an account of some 

 observations of the Geophilus is given, from which it would 

 appear that it used its power of emitting light as a means of 

 protection. It might be well to point out that irritation or ex- 

 citation of many luminous organisms has this result. Even in 

 such low forms as the light-producing bacteria the same efifect 

 can be seen. In a paper on the " Physical Basis of Animal 

 Phosphorescence," by S. Watase, of the University of Chicago, 

 published with the biological lectures delivered at Woods 

 HoU, 1895, a very full account is given of the phenomenon as 

 seen in the ordinary fire- fly, and the process is essentially the 

 same in all light-producing organisms. In some the luminous 

 product of cell metabolism is oxidised in situ, while in others 

 it is thrown out in response to a stimulus as a liquid secretion. 



J. E. Barnard. 



Birds Capturing Butterflies in Flight. 



Mr. Latter still believes the capture of butterflies in flight 

 by birds to be " exceptional so far as this country is concerned " 

 (p. 273). Closer observation would assure him of the contrary, 

 I think. Why is the c.ise he mentions " probably to be 

 regarded as a mistake on the part of the bird," when it is 

 admitted that the captor "only relinquished its hold in conse- 

 quence of a luckily-aimed stick " ? Why assume that the 

 thrower of the stick knew better what the house-martin ought 

 to eat than the bird itself? In July 1900 I saw a house-sparrow 

 in my garden attack a common brown butterfly on the wing 

 (species unidentified). The chase lasted three minutes, by my 

 watch, ill the air the whole time, the butterfly doubling and 

 turning again and again, and the sparrow after it, in a manner 

 most remarkable for a bird without much hovering-power. 



NO. 1683, VOL. 65] 



Eventually both butterfly and sparrow went into a box hedge, 

 and the sparrow came out immediately afterwards, eating the 

 butterfly ; he finished it with much apparent satisfaction on a 

 branch of an apple-tree, and cleaned the scales off his beak on 

 the twig. Sparrows are not, as a rule, insect-eaters, but J. H. 

 Gurney gives, as a result of 694 dissections, under the heading 

 " occasional food," these entries : — 



" August. — Moth of Crambtis c 11 1 melius." 



*'June. — Large brown cabbage-moth (W. Johns)," 

 and adds : ** I have notes of sparrows occasionally feeding on 

 the yellow Underwing, Ermine moth, and a few other insects 

 in the perfect state. . . . Everybody mast, at some time or 

 another, have observed their clumsy efforts to catch some 

 common butterfly" ("The House-sparrow," Gurney, Russell 

 and Coues, pp. li-iS). These notes have the greater value 

 because they occur in a book written with the avowed object of 

 convicting the .sparrows of a diet injurious to the agriculturist ! 



If, therefore, attacks by " occasional " enemies are not in- 

 frequent, why imply that the toll taken by the vast crowd of 

 insectivorous birds "/mist he very slight?" The question is, 

 is it ? Only specially directed observations can answer this. 



Lilian J. Veley. 



20 Bradmore Road, Oxford, January 26. 



Extremes of Climate in the British Empire. 



I H.WE just read the note on p. 87 of your issue of Novem- 

 ber 2S last giving an abstract of the " Summary of the Climate 

 of the British Empire" in Synions^ Meteorological Magazine \ 

 and I think that even though it is expressly said to be only "so 

 far as it can be represented by reports for eighteen stations," 

 such a summary is misleading. Thus, .\delaide is given as 

 having the highest shade temperature, absolutely ignoring the 

 fact that Lahore, with a population 50 per cent, more than 

 Adelaide, has a maximum shade temperature for a month or 

 more at a time rarely falling below 116°, and often well over 

 120" ; while in Jacobabad, a much less important place, it is 

 true, but still a garrison town, the maximum shade temperature 

 in June and July is more often over 120° than under it. 



Again, for maximum rainfall, not to mention Cherra Punji, with 

 an average of more than 400 inches, or many places on the west 

 coast of India and Burmah with averages of 100 to 200 inches, 

 the large town of Rangoon is far wetter than Calcutta. Being 

 far from records here I can only give averages ; but I do not 

 think I am wrong when I say that the places mentioned in your 

 paragraph are hardly typical of the extremes of climate exhibited 

 by even the larger places in the British Empire, which, I take 

 it, should be the object of such a summary. 



Lalitpur, India, January 2. Chas. A. Silberrad. 



A GALLERY OF ANIMAL ENGRAVINGS OF 

 THE STONE AGE. 



THE clever etchings on bone and ivory of the cave- 

 dwellers of western Europe who lived towards the 

 close of the Paljeolithic period are well known to all who 

 interest themselves in the pre-history of man. In 1895 

 M. E. Rivit-re published the first discovery of engravings 

 and pictographs on the sides of a cavern. The second and 

 quite recent similar record is published in the Coiiiptes 

 rendiis of the Paris Academy of Sciences (December 9, 

 1901, p. 1038) by MM. Capitan and Breuil. These 

 archaeologists had the good fortune to discover on the 

 walls of the cave of Combarelles, in the neighbourhood of 

 Eyzies (Uordogne), 109 engraved figures which date from 

 the Magdalenian epoch. .'\11 the figures are engraved 

 upon the vertical walls of the cave for a distance of 

 100 metres on each side of the passage. They reach to 

 an average height of fjO metres, commencing at about 

 15 or 20 centimetres above the ground and often ex- 

 tending to the roof — which, in truth, is mostly low, being 

 only one to two metres in height, but this has been 

 curtailed by stalagmites. 



The figures are mostly deeply graven in the rock, but 

 some designs are merely scratched. Very often they 

 have been coated by a layer of stalagmite which is 



