18 



KNOWLEDGE. 



[January 1, 1898. 



for the extirpation of any peculiar species, why should we 

 seek to extirpate them merely because they appear to be 

 dying out of their own accord ? I would rather preserve 

 them as long as possible. 



The dying out of a race of animals, when natural, may 

 often indicate a gradual change of climate or other physical 

 conditions, the history of which it will be desirable to 

 trace hereafter. The arrival of a new race may afford 

 similar indications to the student of science. But if we 

 ruthlessly shoot down every member of a race that is dying 

 out and every now arrival on our shores, landmarks of this 

 description will be lost. The "footprints on the sands of 

 time " wear out soon enough without intentional oblitera- 

 tion. W. II. S. MONCK. 



[The killing of rare birds has of late formed the subject 

 of innumerable letters in the daily press. These letters are 

 invariably written by persons not suliiciently acquainted 

 with the details of the subject to form an accurate opinion 

 as to whether the killing of any particular bird is to the 

 advantage or disadvantage of the study of British birds. 

 By this we mean that unless certain birds are killed 

 ornithology will not advance. Glance, for instance, at the 

 second part of Mr. Howard Saunders's manual (just pub- 

 lished). There are at least six birds out of the twenty- 

 four there described which would never have been known 

 to have visited the British Islands had they not been shot. 



With regard to the birds mentioned by Mr. Monck, these 

 were all stragglers, and we can confidently say that none of 

 them would ever have bred in Great Britain had they been 

 allowed to live, and certainly three of them would never 

 have been identified unless they bad been shot. We do 

 not wish our readers to infer from the foregoing remarks 

 that we uphold the killing of every rare bird. Far from 

 it. We consider it an act of ignorant greed to destroy in 

 Great Britain a bird such as a Golden Eagle or Osprey, 

 which were formerly fairly plentiful as breeding species, 

 but have now become very rare. We would remind Mr. 

 Monck that the Society for the Protection of Birds, which 

 has often been referred to in Knowledge, has been estab- 

 lished some years, and has done and is doing very good 

 work in the prevention of that very ignorant destruction 

 to which Mr. Monck so properly objects. — Eds.] 



MOVEMENT IX SP.VCK. 

 To the Editors of Knowledge. 



Sirs, — I saw it stated the other day that one of our 

 astronomers had made a calculation that the rate of 

 movement of our sun in space was twelve miles a second. 



This idea of "movement in space" is to me incom- 

 prehensible. What we call " movement " is a relative 

 state of matter, and can only be measured against some- 

 thing " at rest." For instance, we call an object fixed or 

 stationary on the earth, when really it participates in the 

 earth's motion ; so it is quite possible that a fly on the 

 woodwork of a railway carriage may consider itself " at 

 rest " when it pauses in its walk, although the train is 

 travelling at its usual speed. 



As it would appear from our limited knowledge of the 

 universe that a state of absolute rest is impossible, it 

 would be interesting to know how this movement of the 

 sun can be measured with anything approaching accuracy. 



If you consider this a suitable subject to appear in your 

 very interesting magazine, you would much oblige, 



Ignoramus. 



["Ignoramus" is quite right in supposing that motion in 

 space can only be measured by taking some origin which 

 we suppose fixed. In deducing the solar motion we 



assume that the group of stars which we employ for the 

 purpose have, as a whole, no tendency to drift in any 

 direction^or, in other words, that their centre of mean 

 position is at rest. This centre of mean position is thus 

 the fixed origin to which the solar motion is referred. 

 The whole system of stars under discussion, including 

 our sun, may have a common drift in some direction, but 

 this we are unable to determine.] 



Notices of Boolts. 



With y'ature ami a (amern. By Richard Kearton, f.z.s. 

 Illustrated from Photographs by Cherry Kearton. (Cassell.) 

 21s. Perhaps we expected too much of Mr. Kearton, 

 judging from reports which reached us before the publication . 

 of his book. However that may be, we are disappointed. 

 There are many good things in the book, but it is our candid 

 opinion that the author has been too hasty in putting his 

 work before the public, for it bears unmistakable signs 

 of " padding." A number of tlie photographs are not 

 of sutlicient interest for publication, while to others a 

 great deal too much space has been given, making the 

 book large, expensive, and annoying to the reader. The 

 most glaring examples of " padding " are two full-page 

 illustrations of a rabbit burrow closed and a rabbit burrow 

 open (pages 178 and 179), a common enough sight to 

 everyone. If the photographs had been " pictures " we 

 should, perhaps, have excused the author, since his book 

 is mainly a " picture book " ; but they are by no means 

 pictures, and are made additionally hideous by a large 

 bottle in the foreground. The letterpress also is by no 

 means free from " padding." A number of the facts- — 

 some of them here set down as extraordinary— have been 

 published scores of times before. It is well known that 

 the song thrush sings occasionally on fine nights : yet the 

 author, who has had some experience, was " astonished to 

 hear a thrush commence to sing " one moonlight night, 

 and considers that in this fact he has " unmistakable 



proof" that "birds may, upon occasion, mistake the 

 rising of the moon for the coming of another day." The 

 author gives a detailed account of an old shooter and his 

 favourite " setter " bitch, and on page 161 he gives a 



