486 



NATURE 



[March 26. 1896 



OUR BOOK SHELF. 



British Moths. By J. W. Tutt. Pp. xii + 368. Illustrated. 



(London : George Routledge and Sons, 1896.) 

 The last of the many recent additions, superficial and 

 profound, to the stock of books on British Lepidoptera, 

 is essentially a book for the beginner, but one which 

 challenges consideration as an attempt " to deal with 

 our moths on lines which the study of the last twenty- 

 five years has convinced all true naturalists are the 

 correct ones." The points by which this claim is re- 

 deemed consist mainly in the substitution of an arrange- 

 ment based on Dr. Chapman's division of the Lepidoptera 

 by pupal characters for the old order so long accepted, 

 and by numerous statements of phylogenetic relationship. 

 Supported as they are by very little in the way of ex- 

 planation to make them intelligible, these innovations are 

 not so much an improvement as a snare ; it is of no 

 use to talk glibly in a beginner's book about " Obtecta^ 

 and Incompletas," " offshoots from a Pyralid stirps," and 

 the like, unless these things are fully and clearly ex- 

 plained. Much of the phylogeny so confidently put for- 

 ward is not that accepted by other recent writers on 

 Lepidoptera and is unfit matter for dogmatic assertion, 

 especially as first impressions thus acquired are hard to 

 unlearn. Neither is the writer consistent, for the Hepia- 

 lid;ie, Micropterygidte, and Eriocephalida; are separated 

 from each other by numerous families, although the 

 position, remote from all other Lepidoptera, that has 

 been assigned to the three is one of the most im- 

 portant and widely-accepted of recent changes. 

 Turning to those parts of the book which have no 

 special claim to novelty of treatment, we find, as 

 is to be expected from so competent a lepidopterist, 

 that his statements are accurate and often valuable. 

 But far too much space is taken up, particularly in the 

 Noctua;, with brief remarks on species which convey no 

 real information. In spite of another claim put for- 

 ward in the preface, it is only here and there that a 

 species is described in recognisable terms. If all per- 

 functory mention of species had been excluded, and the 

 work confined, as a book of limited scope may well be, 

 to such moths only as are common and of wide distribu- 

 tion, space could have been gained for an adequately-full 

 treatment of the species retained. The coloured illus- 

 trations are fairly good ; there is but one diagram of 

 neuration, and that is incorrect. W. F. H. B. 



Moorland Idylls. By Grant Allen. Pp. 257. (London : 



Chatto and Windus, 1896.) 

 By Tangled Paths. By H. Mead Briggs. Pp. 203. 



(London : Frederick Warne and Co, 1896.) 



The descriptions of scenes of pastoral life contained in 

 the first of these volumes have, we believe, already 

 appeared in one of the monthly magazines, though 

 no reference is made to that fact. They may be 

 regarded as science diluted with sentiment, and that is 

 the kind of literature which the average man and woman 

 will sometimes read. Nevertheless, if Mr. Allen's idylls 

 lead people to observe and think about the habits and 

 characteristics of common plants and animals, they will 

 accomplish a useful purpose. The sympathetic spirit in 

 which they are written will attract lovers of nature, 

 and will do much to foster a feeling for the preservation 

 of our native fauna. 



Mr. Briggs's dainty volume is much the same in 

 character as that of Mr. Grant Allen's, the chief differ- 

 ences being that it is a little more poetical, and a little 

 less instructive. The contents furnish suitable reading 

 for persons who muse over the poetry of nature ; and 

 judging from the abundance of literature of a similar 

 character, there must be many who like to engage their 

 minds on natural things. 



NO. 1378, VOL. 53] 



LETTERS TO THE EDITOR. 

 \The Editor does not hold Jiimself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 mamiscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous coiiiinitnicatio;n.'\ 



Sun Columns at Night. 



A REMARKABLE phenomenon, similar to that which I de- 

 scribed in 1888 (Nature, vol. xxxviii. p. 414), was witnessed by 

 me on the evening of March 13. At 7h. 7m. p.m. I saw on the 

 western sky five silvery white columns coming evidently from 

 the sun, which set at 6h. im. The columns extended over 

 the whole sky, and, like meridians on a globe, converged to a 

 point in the eastern sky, which was about as high above the 

 eastern horizon as the sun was below the western horizon. The 

 sky was full of stars, a powerful wind having swept it clear ; and 

 at 7h. 25m., fifteen minutes before complete night had set in, the 

 rays still reached the zenith. The rays cannot be straight ^\xn rays, 

 for the calculation of the height of the atmosphere by Alhazen's 

 method would yield an abnormally high value, and they could 

 not meet in the east, like meridians, but they must be curved 

 and pass along the upper strata of the atmosphere. This is 

 either due to reflection, or, more probably, the phenomenon is 

 one of an electrical nature, similar to that described in Nature 

 of March 12 (p. 437), which has just reached me, by Dr. 

 O'Reilly. 



The remarkable fact that at 7h. 25m. , when the sun was about 

 14° below the horizon, the perpendicular arc reached the zenith, 

 whereas that passing along the equator extended to about 

 Cancer, appears to prove that the equatorial diameter of the 

 atmosphere greatly exceeds the polar diameter. The pheno- 

 menon disappeared at 7h. 28m. Bohuslav Brauner. 



Bohemian University, Prague, March 16. 



Kathode Rays or X-Rays? 



To the reader of the numerous papers that have recently been 

 communicated from various sources on the subject of Dr. 

 Rontgen's great discovery, considerable obscurity is caused by 

 the confusion of the above terms. Until quite recently what has 

 been meant by "kathode rays "or "the kathodic discharge" 

 has been that discharge of matter from the negative electrode in 

 a highly-exhausted vacuum tube, which can be deflected by a 

 magnet, produce heat, mechanical energy, and phosphorescence, 

 can be brought to a focus by using a curved kathode, and in this 

 case will project an inverted image of the kathode upon either 

 the inside walls of the tube, or upon a phosphorescent screen 

 placed inside the tube to receive it. As is well known, this dis- 

 charge has been very thoroughly investigated abroad by Hittorf^ 

 Puluj, and.others, and in England by Crookes, and has been called 

 by him the discharge of " radiant matter." The X-rays of Dr. 

 Rontgen are said to be generated at the spot where the kathodic 

 discharge of radiant matter impinges upon an obstacle, be it the 

 phosphorescent walls of the vacuum tube, or a plate of metal 

 similarly placed to receive it. The distinction is perfectly clear 

 in Dr. Rontgen's paper, as the following extracts from the 

 translation, published in this journal on January 23, show. 



" In general, other bodies behave like air ; they are more 

 transparent for the X-rays than for the kathode rays. A further 

 distinction, and a noteworthy one, results from the action of a 

 magnet. I have not succeeded in observing any deviation of 

 the X-rays even in very strong magnetic fields. The deviation 

 of kathode rays by the magnet is one of their peculiar 

 characteristics." 



" Hence I conclude that the X-rays are not identical with the 

 kathode rays, but are produced from the kathode rays at the 

 glass surface of the tube." 



" I have obtained them in an apparatus closed by an 

 aluminium plate 2 mm. thick." 



It will therefore surely be better to retain the term proposed 

 by their discoverer. X-rays, or else to call them Rontgen rays, 

 and thus avoid the confusion that must result from calling them. 

 " kathode rays." James H. Gardiner. 



A Remarkable Meteor. 



The slow-moving meteor of March i, 8h. 31m., described by 

 Mr. J. E. Clark at York (Nature, March 12, p. 437), was 

 observed by Mr. T. W. Backhouse at Sunderland, and he noted 



