August 2, 1900] 



NATURE 



Z^^l 



as benzoic acid, toluene, turpentine, &c. At a later 

 date this severe method of treatment was replaced by the 

 milder action of fused potash, with the result that a 

 number of new aromatic acids and phenols were dis- 

 covered. At the present time the separation of the 

 various constituents of a resin is effected by the use of 

 solvents and the numerous reagents which the resources 

 of modern organic chemistry can offer. The results do 

 not carry us very far. As the author says, " our march 

 of conquest has only begun, and the present volume may 

 suggest a successful plan of campaign." J. B. C. 



The Lepidopiera of the British Islands : a Descriptive 

 A ccouni of the Families, Genera and Species Indigenous 

 to Great Britain and Ireland, their Preparatory > tales. 

 Habits and Localities. By Charles G. Barrett, F.E.S. 

 \'ol. vi. Parts 59-70. Heterocera (Noctuina — Geo- 

 metrina). Pp. "388. Plates 233-280. (London : 

 Lovell, Reeve and Co., Ltd., 1900.) 



The present instalment of Mr. Barrett's great work in- 

 cludes 1 10 species, from Hoporina croceago, Schiff., to 

 Halix wauaria, L., and is written in the same exhaustive 

 manner as previous volumes, giving all the information 

 that a collector of British Lepidoptera (as such) is most 

 likely to require. To Continental entomologists who 

 wish to acquire an accurate knowledge of our limited 

 insular fauna it would also prove very useful ; though it 

 is to be regretted that the bulk of the book, which may 

 be expected to extend to nearly twenty volumes, and the 

 unavoidable costliness of the larger edition issued with 

 plates (which are not included in the cheap edition), 

 must necessarily tend to restrict the sale. Those re- 

 quiring it may therefore be recommended to obtain it 

 volume by volume, or in monthly parts, as it appears, 

 rather than to wait till the whole work is completed. We 

 need not repeat our comments on earlier volumes, which 

 will equally apply to the one before us ; but the accounts 

 given of the habits of the various moths discussed are 

 always interesting, and sometimes curious ; thus we learn 

 that the rare Cerastis erythrocephala, Schiff., after its dis- 

 covery in 1847, was met with occasionally till 1859, when 

 it seems to have almost disappeared till 1872 and 1873, 

 since when only one specimen, taken in 1894, has been 

 found in England. The periodicity of the appearance of 

 many species in these islands is curious, and has never 

 been fully explained, for the causes which appear appli- 

 cable to some cases will not explain others ; and, more- 

 over, uncertainty in the appearance of species seems to 

 increase rather than to diminish. English names are not 

 a conspicuous feature in this book, but Mr. Barrett notes 

 that a recent writer has called Xylina con/ortnis, Schiff., 

 ''The Conformist," and the next species, X. lambda, Fab., 

 "The Nonconformist" I The resemblance of species 

 of Calocampa and Cticullia to bits of stick is commented 

 on ; in fact, certain moths and larvae thus fill the gap in 

 our protected fauna caused by the absence of the stick 

 insects proper, or Phasmidie, which are not found nearer 

 to our shores than the South of France. Several species 

 noted in this volume seem to be now extinct in our 

 islands ; thus, Chariclea delphinii, L., does not seem to 

 have been taken in England since about 181 5. Their 

 place has been taken by others ; for example, the 

 northern migration of Plusia inoneta. Fab., reached 

 England in 1890, and is probably still extending. Other 

 moths of interest are those with cannibal larva;, such as 

 Scopelosoma satellitia, L., Heliothis arinigera, Hiibn., &c. 

 There are many other interesting observations, which we 

 have no room to quote, in the present volume, comprising, 

 as it does, the conclusion of the Noctuae, the Deltoidre, 

 and the first few species of the Geometrte. We may, 

 however, note that the enigmatical Sarrothripa revayana, 

 Schiff., is regarded by Mr. Barrett as a true Noctua, and 

 is placed at the end of the Noctuae Trifidae. 



W. F. K. 



NO. 1605, "^'OL. 62] 



LETTER TO THE EDITOR. 

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

 pressed 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 «/ Naturf. 

 No nonce is taken of anonymous communications, "l 



The Plankton of the Bay of Biscay. 



With the valuable assistance of Mr. L. A. Borradaile, of 

 Selwyn College, Cambridge, I have just completed a series of 

 observations on the plankton of the Bay of Biscay extending 

 over about three weeks, by means of opening and closing nets, 

 as well as ordinary tow-nets. Our observations point to the 

 fact (unexpected at any rate by myself) that the smaller Meso- 

 plankton practically ceases at a depth of about 1000 fathoms. 

 This conclusion agrees with that reached by Prof. Chun on the 

 basis of the Valdivia Expedition (Deutsche Tiefsee Expedition, 

 1898-99, p. 44), with which, however, we were unacquainted 

 until we had arrived at it independently. Below this limit we 

 almost always captured a few specimens, as to which it wms 

 doubtful whether they were alive when captured, or were merely 

 corpses of a shallower fauna sinking to the bottom, but in a 

 few cases we at present incline to assign them to a living 

 Mesoplankton. 



We have also taken about 90 hauls under varied conditions 

 at varied depths between 100 fathoms and the surface, which 

 will eventually, we hope, give a fairly accurate basis for the 

 determination of the vertical movements of the Epiplankton. 



Our thanks are due to the Lords Commissioners of the 

 Admiralty for placing the ship at our disposal, and to Captain 

 Field and the other officers of the Research for their ungrudging 

 assistance. G. Herbert Fowler. 



H.M.S. Research, Devonport, July 27. 



THE TEACHING OF MATHEMATICS. 



I THINK it very important to try to get a view of our 

 system of teaching mathematics which is not too 

 much tinted with the pleasant memories of one's youth. 

 Like all the men who arrogate to themselves the right to 

 preach on this subject, I was in my youth a keen geo- 

 metrician, loving Euclid and abstract reasoning. But I 

 have taught mathematics to the average boy at a public 

 school, and this has enabled me to get a new view. I 

 have seen faces bright outside my room become covered 

 as with a thin film of dulness as they entered ; I have 

 known men, the best of their year in England in classics, 

 lose in half an hour (as men did in the first day of 

 slavery in old times) half their feeling of manhood ; and 

 I have known that, as an orthodox teacher of mathe- 

 matics, I was really doing my best to destroy young 

 souls. Happily, our English boys instinctively take to 

 athletics as a remedy, and I know of nothing which 

 gives greater proof of the inherent strength, in good 

 instincts and common sense, of our race than this refusal 

 to allow one's soul to be utterly destroyed. I have also 

 mixed much with engineers, who really need some 

 mathematics in their daily work, men who say that they 

 once were taught mathematics, and I know that these 

 men never use anything more advanced than arithmetic, 

 and actually loathe a mathematical expression wheii it 

 intrudes itself into a paper read before an engineering 

 society. Of all branches of engineering, electrical 

 engineering relies most upon exact calculation. Well, 

 the average electrical engineer in good practice would 

 rather work a week at many separate arithmetical ex- 

 amples than try for an hour to get out the simple 

 algebraic expression, which includes all his week's re- 

 sults and much more. Yet he has passed perhaps 

 certain rather advanced examinations in mathematics. 

 Furthermore, those engineers who can most readily 

 apply mathematics to engineering problems, almost in- 

 variably descend to the position of teachers and pro- 

 fessors in schools and colleges, and they seem to lose 

 touch completely with the actual life of their profession. 



