304 



NATURE 



[June 20, 19 18 



LETTERS 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. No notice is 

 taken of anonymous communications.'] 



The Food of the Rook. 



Is there not even a fallacy in the argument against 

 this bird which is supported by a note in Nature of 

 June 6, p. 271? You say that because 52 per cent, of 

 the rook's food is injurious, 195 per cent, neutral, and 

 285 per cent, beneficial, therefore "it is impossible 

 to ignore the fact that at present this bird does 

 considerably more harm than good," even though, as 

 you admit, 239 per cent, of the rook's food consists 

 of injurious insects. 



Is it riot possible that if tiiese injurious insects; — 

 they doubtless consist of many species — had been left 

 unconsumed by the rook, they might have so multi- 

 plied that their total depredation upon man's food 

 supply would have considerably exceeded the 52 per 

 cent, of foodstuffs which the bird consumes directly? 



As a method more likely to restore the balance of 

 Nature than the indiscriminate destruction of certain 

 species of birds, the rook included, I would suggest 

 a strict preservation of all our birds of prey ; and now 

 that game-preservation has to take second place to 

 food production, this would seem to be a matter for 

 practical legislation. Sydney H. Long. 



Norwich, June 10. 



If Dr. Long assumes that the 239 per cent, of 

 injurious insects left unconsumed might have multi- 

 plied, it is surely only fair that he should also assume 

 that, under similar conditions, the 485 per cent, of 

 cereals, potatoes, and roots would have multiplied 

 and brought forth a hundredfold. The point at issue, 

 however, is whether, in estimating by the volumetric 

 method the amount of food consumed by the rook per 

 annum the figures express equivalent or economic 

 values. This method has so long been recognised as 

 the only trustworthy one that it is not necessary to 

 reassert its superiority over all others ; and as Mc.^tee 

 lias so pertinently remarked (The Auk, 1912, 

 p. 452), such " criticisms are w'ide of the mark, for 

 no one claims that percentages do express economic 

 values. They are simply convenient handles to facts, 

 and they must be interpreted." As the result of long 

 f xperience and the examination of the alimentary 

 system of upwards of two thousand rooks, by which 

 we have obtained the percentages referred to, viz. 

 tliat of the food consumed by the rook during a whole 

 year, 52 per cent, is injurious, 19-5 per cent, neutral, 

 and 28 j:; per cent, beneficial, our interpretation ' of 

 these figures, in the light of a long experience as to 

 the detailed nature of the food under each heading, 

 leads us to the conclusion that this bird does con- 

 siderably more harm than good. 



The advisabilitv of practical legislation for the strict 

 preservation of birds of prev and the relationship of 

 such to game-bird preservation is a very complicated 

 subject. All statistics, however, go to prove that the 

 preservation of game-birds is beneficial rather than 

 -inimical to food production, and there are manv other 

 ■^idts of the Question which Dr. Long does not seem 

 tm have considered. The Writer of the Note. 



A Proof that any Aggregate can be Well-ordered. 



I\ my letter printed in Nature for April 4, 1918 

 (vol. ci., p. 84), the class of direct continuations used 

 for well-ordering should have been stated to be " com- 



! plete" — that is , to say, no chain of M outside the 

 I class is such that every member of this class is a seg- 

 ! ment of this new chain. The actual construction of a 

 I complete class of direct continuations can be carried 

 out in a perfectly unique manner throughout in terms 

 of the possible chains of M, without assuming that 

 , there is any chain of M that exhausts M itself. This 

 construction is given in detail in a paper which will 

 shortly appear in the Comptes rendus, and the detail 

 of the consequences of the existence thus proved has 

 already appeared in the Comptes rendus for April 2. 

 Philip E. B. Jourdain. 

 The Bourne, Basingbourne Road, 

 Fleet, Hants, May 31. 



Construction for an Approximate Quadrature of the 

 Circle. 



I The construction for squaring the circle given by 



Mr. R. E. Baynes in Nature for June 6 was described 



more fully by Mr. T. M. P. Hughes in the issue for 



j April 2, 19 1 4, with a simple extension to the repre- 



I sentation of the circumference. 



, Mr. Hughes suggested the use of a permanent set- 

 : square of the proper angle, and it seems that the 

 ; method was known earlier, for in the Science Museum 

 : at South Kensington I have seen a set-square for the 

 purpose. I did not examine it carefully, but I believe 

 j it bore the inscription " Edward Bing, Riga, 1876." 

 I Perhaps someone else may know the history of this 

 j instrument and method. Glenny Smeal. 



1 University of Edinburgh, June 8. 



There are in the Science Museum three examples 

 of the set-square to which Mr. Smeal refers. They 

 have been here since 1876, in which year they were 

 lent by the inventor, Edward Bing, a member of the 

 staff of the Waggon Works at Riga, for exhibition 

 in the Special Loan Collection of Scientific Ap- 

 paratus. There is a short description in the third 

 edition of the catalogue of that collection, published in 

 1876, at p. 14, and I have no record of any earlier 

 published description. One of the examples is of steel 

 and the other two of wood, the hypotenuse in 

 each case being about 7! .in. long. The inventor's 

 MS. label inside the mahogany case containing the 

 steel set-square reads : — " Bing's Circular Square. 

 Kreiswinkel. Equeire circulaire. Cosinus a = Vn'^. 

 (0 = 27^ 35' 49-636")." David Baxandall. 



The Science Museum, . 



South Kensington, June 13. 



INTER-ALLIED SCIENTIFIC FOOD 

 COMMISSION. 



IN a recent speech Mr. Clynes stated that the 

 events of the last two years had revealed the 

 necessity, not only of securing complete unity of 

 action among the Allies, but also of basing any- 

 such action on the guiding principles laid down by 

 science. This recognition of the fundamental part 

 which science should play in the successful direc- 

 tion of public affairs is noteworthy as coming 

 from a member of the youngest of our political 

 parties, and augurs well for the future of the 

 country when this party comes to be entrusted with 

 a responsibility commensurate with its political 

 power. In fact, much of the success of the 

 Ministry with which Mr. Clynes is connected may 

 be ascribed to the adoption by Lord Rhondda of 

 a policy based on the collective 'experience of 



NO. 2538, VOL. lOl] 



