June i, 1893J 



NATURE 



101 



able to accomplish it within a reasonably short period. 

 As a matter of fact, he says, the enterprise " has taken 

 me as many years to finish as I expected it would have 

 taken months.'' The " Index'' does not relate to all the 

 papers published by Gould in various journals, but it does 

 include every work which he issued separately, whether 

 in folio, or octavo, or quarto form ; and Mr. Sharpe, with 

 the aid of his assistant at the Natural History Museum, 

 has been careful to check the various references, the num- 

 ber of which is nearly seventeen thousand. He has also 

 put in some " extra synonyms from popular works, such, 

 for instance, as Oates's ' Birds of British India,' which in 

 a few years will have familiarised Indian naturalists and 

 sportsmen with a certain set of names which do not occur 

 in Gould's works, though the species may be duly 

 figured therein." The work, which is very handsomely 

 "got up," will be of great value to all who are fortunate 

 enough to possess Gould's writings, and it will frequently 

 be of good service to every serious student of orni- 

 thology. In the biographical memoir Mr. Sharpe not only 

 presents the leading facts of Gould's career, but has 

 much that is fresh and interesting to say about the results 

 of his scientific labours and about the essential qualities 

 of his character. 



An Elementary Treatise on Pure Geometry, with numerous 

 examples. By J. W. Russell. (Oxford: Clarendon Press, 

 1893-) 

 The opening sentence of the Preface — " The author has 

 attempted to bring together all the well-known theorems 

 and examples connected with Harmonics, Anharmonics, 

 Involution, Projection (including Homology), and Recipro- 

 cation " — indicates that the writer has given himself a 

 "tall order." Within the limits of 323 pages we have 

 here collected every possible property that a student can 

 desire to have. Our only objection to the book is that 

 it is too full for ordinary purposes, but as the matter is 

 put together with considerable skill and ability —thus 

 evidencing the writer's familiarity with, and mastery 

 over, his subject — and illustrated with a choice collection 

 of worked-out exercises, we cordially commend it. We 

 could wish that a handbook for school use were founded 

 upon it. There used to be a rumour abroad that the 

 late Prof. Henry Smith intended to publish his Geomet- 

 rical Lectures. That hope is now, we presume, frus- 

 trated, but as Mr. Russell's first lessons in Pure Geometry 

 were learnt from Mr. Smith's lectures, and as many of 

 the proofs of the present work are derived from the 

 same source, we must possibly take it as the substitute 

 for the " Geometrical Lectures." The get-up of the te.xt 

 is on the usual lines of the Clarendon Press and is all 

 that one could desire. 



Sun, Moon, and Stars: Astronomy for Beginners. By 



A. Gilberne. (Seeley and Co., Limited). 

 This small book comprises 300 pages of matter, and 

 contains a most interesting account of the various 

 members of the solar system and other celestial objects 

 more remote. The narrative is particularly adapted to a 

 large class of people who desire to know somewhat of 

 the wonders and awe-inspiring phenomena connected 

 with the science of astronomy without making a special 

 study of them ; yet sufficient interest is aroused to 

 induce a beginner to search for more information. The 

 work, however, does not claim to be a text book, 

 although to a beginner it will serve as a capital starting- 

 point. It is printed in open and pleasing type, 

 and contains instructive illustrations. A few passages 

 might be somewhat improved upon, as for example, 



P- '43- 



" It is said that a cannon-ball, reposing on the 

 sun, if lifted one inch and allowed to fall, would dash 

 against the ground with a speed three times greater 

 than that of our fastest express-trains." 



NO, 1231, VOL. 48] 



LETTERS 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 op Nature. 

 No notice is taken of anonymous communications ."[ 



Mr. H. O. Forbes's Discoveries in the Chatham Islands. 



Unwilling as I am to interpose in the discussion between 

 Mr. Wallace and Mr. Forbes (supra pp. 27, 74), yet each of 

 those gentlemen having referred to opinions formerly expressed 

 by my brother and myself, it seems fitting that I should offer a 

 few words on the present occasion, if it were only to avoid mis- 

 apprehension ; but I would premise that I have not seen Mr. 

 Forbes's paper read before the Geographical Society or his 

 article in the Fortnightly Review. To this I would add that I 

 am no more ashamed of opinions in the utterance of which 

 before the Royal Society in 1868 I took a share, than I am of 

 having then been a quarter of a century younger than I am now. 

 Whether they are to be considered modified by what I published 

 some halfdozen years later, when I next touched upon the 

 subject, I do not greatly care, and leave to the judgment of those 

 (if any there be) who may take the trouble of comparing the 

 '^&%%^ge.\n\h& Philosophical Transactions (1869, pp. 357.358) 

 with that in the " Encyclopxdia Britannica " (ed. 9, iii. p. 760); 

 and what I now think, or at least thought some eighteen months 

 ago, when the last thing I wrote on the question was passed for 

 press, will I hope be before the public in October. 



However I would point out that one thing seems needed to 



make this discussion real, and that is proof of the assertion, 



made in Nature — at first tentatively (xlv. p. 416), then 



positively [torn, sit., p. 580), and again with fuller details (xlvi. 



p. 252), that Aphanapteryx ever inhabited the Chatham Islands. 



Mr. F'orbes has been so kind as to show me on two occasions 



the bones which he ascribed to a species of that genus, and I 



was fortunately able to let him compare them with those of the 



real Aphanapteryx in the Museum of this University, being all 



that have as yet been recovered from Mauritius. I pointed out 



to him differences between the remains of the two forms which 



appeared to me of generic value, and I thought I had satisfied 



him on this score, since he did me the honour of asking me to 



i suggest a new name for the form which he had discovered. In 



j that view I was confirmed by finding that, shortly after his last 



! visit to Cambridge, he described the Chatham-Islands bird as 



'' Diaphorapteryx at a meeting of the British Ornithologists' Club 



i on 21 December, 1892, as I learn from its printed Bulletin (No. 



' IV. p. xxi.). All this would matter little to any but specialists did 



! it not seem that what Mr. Wallace rightly terms a "tremendous 



hypothesis" is based on the asserted existence of Aphanapteryx 



\ in the Chatham Islands, and I understand that, on the strength 



of the assertion, further daring speculations have been indulged 



in, to support which Purple Waterhens, extinct or expiring 



Starlings, and what beside I know not, have been dragged in. 



Whether the additional evidence is worth anything remains to be 



seen; but though I fully recognise the importance of Mr. Forbes's 



discoveries, rightly interpreted, we are as yet without proof that 



Aphanapteryx inhabited any part of the New Zealand Region ; 



and if it did not, then as regards the speculations based upon it 



cadit qtuestio. ALFRED NevvtoN. 



Magdalene College, Cambridge, 27 May. 



The Fundamental Axioms of Dynamics. 



Referring to my previous article in Nature on the above 

 subject (May 18, vol. xlviii. p. 62), there are a few explanatory 

 remarks which may be usefully made, — most of them suggested 

 by the recent discussion at the Physical Society, especially as 

 summarised by the President (Prof. Riicker). 



There seems to be some feeling against the advisability of 

 ascending successive steps in a ladder of reasoning unless 

 there be already some perception as to what is to be met 

 with on the top. If the ladder shows signs of ending in a 

 medium of unknown and in some respects paradoxical properties, 

 that fact appears to be felt as an inducement to mistrust the 

 steps which lead thither. 



But it must surely be admitted that if each rung is in itself 

 firm and strong, and if successive rungs follow one another with 

 a reasonable amount of sequence, then we ought fearlessly to 



