April 22, 1886J 



NATURE 



583 



brane. The effect of this when the sound-producing motion set 

 in was to cause the membrane to wrinkle sharply towards the 

 point of convergence ; and, by experiment on the dead insect 

 with the point of a pencil, it was easy to see that the sound was 

 simply produced by this sharp wrinkling of the membrane. If 

 a piece of stiff paper or parchment be held in the fingers, and 

 the thumb be made to play sharply and rapidly upon it in suc- 

 cession, so as to produce a "kink" or wrinkle each time, a 

 very fair representation of the sound of the insect will be pro- 

 duced. A captive insect, when the motion is slowing down, 

 can be advantageously watched ; it will then be seen that, as 

 the sound divides up into separate clicks, the membrane becomes 

 alternately wrinkled and flat. Beyond doubt the sound is no 

 humming. C. S. MiDDLEMiSS 



North- West Himalaya, March 14 



Ferocity of Animals 



I HAVE read with interest the article by Prof. Lloyd Morgan 

 " On the Study of Animal Intelligence " in the present number 

 of Mind, in which he touches upon the subject of entangling fact 

 and inference which attracted my attention when reading 

 " Mental Evolution in Animals " some time since. 



I write to call Prof. Morgan's attention to the excellent 

 example of " ejective inference " given by Dr. Romanes in his 

 letter in Nature for April i (p. 513), where he says of a rat 

 that he "perfectly understood my object." Would it be 

 troubling Dr. Romanes too much to ask him to explain the 

 appearance a 7m/</ rat presents on "perfectly well understand- 

 ing " the object of a human being's actions ? 



Churchfield, Edgbaston, April S F. H. Collins 



Tropical Dew 



Having had occasion to lay out a large quantity of iron hoes 

 and picks, without handles, on the hard ground of an open in- 

 closure in one of the driest districts in India (Bellary), where, 

 in fact, these implements had been collected in the face of a 

 scarcity, it was found, after they had Iain a couple of months, 

 that a thick, weedy, but luxuriant vegetation had sprung up, 

 enough, though there had been no rain, to almost hide the tools. 



The effect depositing tools on giass has had in stimulating its 

 growing the writer has observed in the tropics before, but was 

 at a loss to account for it, except upon some irresolvable 

 theory of radiation or magnetism. 



The whole phenomenon is cleared up by Mr. Aitken's paper 

 on "Dew" in Nature of January 14 (p.256), dew being proved 

 deposited, not, as generally thought, from the air above, but 

 rising and conden-ing from the soil below ; and the ground in 

 India is always hygroscopic. The outer surfaces of the iron 

 tools radiate of course quickly at night, and the stratum of air 

 inclosed between the metal under surfaces and the earth is 

 therefore saturated with condensing moisture. 



That iron giatings laid on bare ground will raise a rank vege- 

 tation in places with only 10 or 15 inches of annual rainfall, and 

 exposed to tropical heat, is a not unimportant fact, as being a 

 readily available substitute for irrigation water, worth further 

 investigation. A. T. Fraser 



India, March 26 



The Climbing Powers of the Hedgehog 



I AM advised by some of my friends to send you a notice of 

 the mode in which hedgehogs may frequently escape from con- 

 finement, and of their habits. 



I obtained a hedgehog last week, and put it in my kitchen. 

 Every day it is placed in a small back area, about 12 feet square, 

 during the day-time. The waste-pipes from the cisterns discharge 

 into this area, and the animal frequently lies under these, and, 

 as my servant says, "wallows in the trough like a pig." If he 

 hears any noise he at once runs to a corner and rolls himself up. 



On Wednesday the servant found him on the top of the parti- 

 tion wall between my area and the next. This wall is vertical, 

 height 9 feet 6 inches. The top course but one projects I inch, 

 so he must have climbed over this. 



He has been watched in the operation. He climbs by the pro- 

 jecting mortar beds, which are rather rough, looking about him fre- 

 quently to see if he is watched. He climbs up the house wall beside 

 the pipe in the corner — an ordinary iron rain-pipe ; but from 



the shoulder of the pipe, where it passes through the wall, to 

 the top of the partition w all, there is a distance of g inches 

 without any pipe, so up this portion and over the projecting 

 brick course he must have climbed by clinging to the wall of the 

 house or the partition wall. 



Yesterday (Thursday) he repeated the ascent, and descended 

 into the next area, where he was found this morning. 



Robert H. Scott 



6, Elm Park Gardens, April 16 



STARS WITH BANDED SPECTRA 1 



nPHE spectroscopic survey of the northern heavens, un- 



■'■ dertaken conjointly by MM. Vogel and Dun^r in 1879, 

 has already progressed so far that its general results can be 

 fairly anticipated — its immediate results, that is to say ; 

 for it is ultimately designed, not so much for a collection 

 of statistics, however valuable and interesting, as for a 

 criterion of change. This effect, however, must wait for 

 the future — perhaps a remote future — to develop ; we can 

 in the meantime gather much present knowledge through 

 labours inspired by still unfolded possibilities. 



The first instalment of the first spectroscopic star- 

 catalogue systematically executed, was published by 

 Vogel in 1883 {Publicationen des astrophysikalischen 

 Observatoriums zu Potsdam, No. 11). It covers a zone 

 of the heavens extending from — 2" to + 20° of declination, 

 and includes 4051 stars down to 7'5 magnitude. M. 

 Duner now sends us from Lund, in a catalogue of 352 stars 

 ftiUy ascertained to possess spectra of the fluted and zoned 

 types, a work of special and extreme importance. 



Stars with banded spectra fall into two perfectly dis- 

 tinct classes, of which the first is well exemplified in 

 a Orionis (Betelgeux), the second in a 5'5 magnitude star 

 close behind the Great Bear, numbered 152 in Schjellerup's 

 Catalogue of Red Stars {Aslr. A/ach., No. 1 591), and 

 called by Father Secchi " La Superba," from the extra- 

 ordinary vivacity of its prismatic rays. The spectrum of 

 Betelgeux (Fig. l) shows a series of seven or eight well- 

 marked dark bands (besides minor shadings) all abruptly 

 terminated towards the violet, and dying out by insensible 

 gradations towards the red. The impression upon the 

 eye resembles that of a colonnade thrown into strong 

 relief by a vivid side-illumination. Only three conspicuous 

 dark spaces, on the other hand, interrupt the beams of 

 152 Schjellerup (Fig. 3) ; but their breadth is fully twice 

 that of the flutings in the spectrum of a Orionis ; and, 

 still more remarkable, ihey fuce in the opposite direction. 

 Their obscurity deepens slowly downwards towards their 

 less refrangible sides, tlien suddenly, by a sharp transition, 

 and with a singular and splendid efiect of contrast, gives 

 place to unclouded light. 



The stars characterised by these two different qualities 

 of absorption, respectively constituted Father Secchi's 

 third and fourth spectral orders. M. Vogel, however, saw 

 fit in 1S74 [Astr. Nach., No. 2000) to modify the arrange- 

 ment by grouping the two varieties together as sub- 

 divisions of a single clasi. Nor was this a mere arbitrary 

 change. It was the outcome of a far-reaching speculation 

 regarding the course of development taken by the great 

 army of suns marshalled in the profundities of space. 



Secchi's classification involved no hypothesis of any 

 kind ; it was founded simply on appearances. But the 

 idea that the colours, consequently the spectra of stars, 

 may guide us to a knowledge of their comparative " ages," 

 thrown out in a crude shape by Zollner in 1865, had, 

 meantiine, made its way. Vogel's adoption of it as a 

 means of rationalising observed particulars, gave it (per- 

 haps prematurely) a recognised scientific status. 



According to this view, the white stars forming Secchi's 

 first order (of which Sirius and Vega may be taken as 



1 "Sur les Etoiles h Spectres de la Troisieme Classe." Par N. C. Dun^r. 

 Memoire presenu! a I'Academie Royale des Sciences de Suede, le 11 Juin, 

 1S84. (Stockholm, 1S84.) 



