September 6, 1906] 



NA TURE 



465 



ciiiKiption of that bone, viz. that it is of costal origin, 

 hul the evidence on which he bases his conclusions 

 is not convincin}^-. For three of the studies Prof. 

 Youn.u: is cither in part or wholly r(S[X)nsibl(', and he 

 is to be confjratulalcd on the vigour shown by the 

 Manchester school of anatomists. 



Rrfniktioiistalchi. By Dr. I., de Ball, Direktor dor 

 v. Kuffncrschcn .Surnwarlc Pp. .\iv+ i8. (Leip- 

 zig: W. Engclinann, icjod.) Price 2.40 marks. 

 The methods of computing corrections for atmo- 

 spheric refraction have always been more or less un- 

 satisfactory, 'ilie conditions of the problem do not 

 lend themselves to extreme accuracy on account of 

 the uncertainty of the meteorological elements intro- 

 duced. The determination of the density of the atmo- 

 sphere at any precise moment, dependent as it is on 

 the temperature, the amount of aqueous vapour pre- 

 sent, and other conditions, is not simple, and custom 

 and authority alike have .sanctioned the employment 

 of rough and approximate data. Bessel's tables, so 

 long in use, were admittedly founded upon inadequate 

 material, and probably would have long" since been 

 superseded but for the inconvenience that arises when 

 any breach of continuitv occurs in a long series of 

 observations; but in observatories where measures 

 of zenith distance have been made at small altitudes 

 this inconvenience has had to be faced. At Green- 

 wich, for example, corrections to Bessel's tables, or 

 .Airy's modifications of them, have been alternately 

 introduced and rejected in the treatment of observ- 

 ations at large zenith distances. 



In the tables which Dr. L. de Ball has issued the 

 dilViculty of continuing an unbroken series of correc- 

 tions, available from the zenith to the horizon, has 

 not been attempted. The tables as arranged are 

 available up to 75° zenith distance, and within this 

 limit represent a consistent theory, that of M. Radau. 

 The form in which the tables are constructed gives 

 the log. of the refraction presumably correct to four 

 places of decimals. In the example worked out it 

 has been necessary to take out five significant integers, 

 and, if the second decimal place is to be correct, this 

 may b? rather a severe strain on four-figure logs. ; but 

 Dr. L. de Ball gives verv good and sufficient reasons 

 for not extending the tables beyond these limits. He 

 reminds us that the determination of the temperature 

 of the air is not so easy as the reading of a thermo- 

 meter seems to suggest. The thermometer bulb is 

 affected bv the heat rays emitted by the objects which 

 surround it, whilst the air absorbs onlv a part of those 

 rays. On these grounds the temperature indicated bv 

 the thermometer may easily differ o°-2 C. from that 

 of the atmosphere, and such a difference would 

 occasion an error of three units in the fourth decimal 

 of the log. of the density, and a similar amount in 

 the log. of the refraction. The tables aim at givin.g 

 an accuracy which is sufficient and practical rather 

 than making a claim to extreme and misleading 

 rio-our. .\ further proof that the author has con- 

 sidered the practical side is shown bv the fact that he 

 has included tables designed to assist the computation 

 of differences of refraction, applicable to the reduction 

 of heliometer and photographic observations. 

 The BiitterjUes of the British Isles. By Richard 

 .South, F.E..S. Pp. X + 204. (London : Frederick 

 W'arne and Co., 1906.) Price 6s. net. 

 XoTwniisiANDiNG the large number of books relating' 

 to British butterflies, there was still room for a 

 pocket handbook which should do for the present 

 generation what Coleman's " British Butterflies " 

 did for the last, and this want Mr. South has set 

 himself to provide. He has succeeded in giving us a 

 portable little book, well up to date, containing full 



NO. 1923, VOL. 74I 



information about structure, transformation, settings 

 &:c., besides a good account of the individual species.. 

 The plates contain coloured figures of the butterflies. 

 on one side of the page, and plain figures of cater- 

 pillars, &c., on the back, thus doubling the number 

 of page illustrations without adding to the thickness 

 of the book. The illustrations in th<r text are nearly 

 all in the introduction. They are uncoloured, and 

 some of them are taken from Sharp, .Auriviliius, 

 and other trustworthy authorities. 



Mr. South admits sixty-eight species as British, 

 but regards only fifty-seven of these as actual natives; 

 but surely, though some of the remainder are extinct, 

 and others only casual visitors, the black-veined white 

 (once abundant, but now almost extinct in England), 

 and the red admiral, still one of the commonest of 

 the Vanessidas, ought to have been included among 

 the genuine natives. The evidence against the red 

 admiral being a genuine British species seems to 

 rest on the assumption of its being a migrant, 

 though this is admittedly not proved, as it is 

 abundantly in the case of its nearest ally, the painted 

 lady. 



The rapid disappearance of butterflies in England 

 is doubtless largely due to the wholesale clearing 

 away of the weeds and plants on which the cater- 

 pillars feed, bv the utilisation of every scrap of waste 

 ground. Yet this cannot be the only reason, or the 

 black-veined white, which feeds on hawthorn as well 

 as on fruit trees, would not be disappearing. In this 

 case the disappearance of the butterfly seems to be due 

 to the increase of insect-eating birds. Every fresh 

 book on butterflies records the increasing scarcity 

 of many species once common, and there are only a 

 few, such as the clover-feeding clouded yellows, which 

 are more plentiful now than in former days. 



In the case of the smaller and more variable butter- 

 flies, a considerable number of varieties are figured 

 (sometimes as many as seventeen on one plate), and 

 we think that most entomologists who are interested 

 in British butterflies will find Mr. .South's little book 

 a very useful supplement to any they may already 

 happen to possess on the same subject. 



W. F. K. 



LETTER TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

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

 manuscripts intended for this or any other part of Nature. 

 Xo notice is taken of anonymous communicatio^is.] 



The Latest Critic of Biometry. 

 Mk. J. J. Lister in his presidential address to Section D 

 at the British Association felt it his duty to go somewhat 

 out of his way in order to urge on biomelricians " that the 

 old adage should be borne in mind recommending that 

 before beginning culinary operations it is advisable first to 

 catch your hare, in other words, to make sure that the 

 problem you seek to elucidate is sound from the stand- 

 point of biology before bringing a formidable mathematical 

 apparatus into action for its investigation " (N.mure, 

 .August 16, p. 400). The importance of the occasion no 

 doubt prevented Mr. Lister from illustrating his criticism ; 

 he had much else to deal with, and he probably hoped that 

 his words without detailed proof would have all the weight 

 which attaches to presidential utterances. These are not 

 made without careful thought and proper study. But in 

 order that a criticism of this kind should be effective, 

 biometricians need more information, and they recognised 

 that Mr. Lister could hardly refuse to cite instances of the 

 type of work which led to his advice. 



Hoping that we might profit by Mr. Lister's caution, I 

 wrote to him as soon as I read his paper in your columns 

 asking for definite instances upon which we tnight consider- 

 how to amend our courses. He has kindlv consented to 



