228 



NATURE 



[October 28, 19 15 



of view. It is divided into five chapters, the first 

 two being- concerned with the coal itself, the 

 second two with the products, namely, oil tests 

 and gas analysis, and the final chapter with fan 

 and ventilation tests. 



The volume has evidently been put together with 

 great care by its authors, who have had practical 

 experience of their subject. The description of the 

 apparatus and methods is clear and concise, and 

 illustrated by diagrams and by actual examples, so 

 that the student should have no difficulty in carry- 

 ing out the different operations. J. B. C. 



OUR BOOKSHELF. 



Some Frontiers of To-morrow : An Aspiration 

 for Europe. By Prof. L. W. Lyde. Pp. viii 

 + 120. (London: A. and C. Black, Ltd., 

 1915.) Price 2s. 6d. 

 Ix this small volume Prof. Lyde makes sugges- 

 tions for the settlement of European frontiers 

 after the war. Three considerations are laid down 

 as of vital importance : (i) that the frontier 

 should be associated, not with war, but with 

 peace; (2) that the unit of area should have some 

 direct relation to national sentiment ; (3) that 

 inability to assimilate should disqualify any Power 

 for territorial expansion. The first suggestion is 

 the most important. Prof. Lyde maintains that 

 frontiers should be identified with features re- 

 lated to the meeting of people in the ordinary 

 routine of peaceful intercourse. If this be true, 

 it follows that a navigable river makes the best 

 frontier. A defensive frontier — the type of frontier 

 of the past — will never put an end to conflict 

 between neighbours, but may even promote it. 

 An inhabited, in contrast to an uninhabited, fron- 

 tier belt encourages contact between adjoining 

 people, discourages racial and cultural antagon- 

 ism, and so minimises the chance of friction, and 

 promotes civilisation. Prof. Lyde is always 

 stimulating, even if he fails to convince at times. 

 His book is crammed with ideas from beginning 

 to end, which should attract the attention of 

 statesmen. But it will be hard to convince those 

 who have treaty making in their hands that 

 accurate scientific knowledge is a real asset in 

 the matter, and that the geographer is the expert 

 who has the knowledge and should be consulted. 



R. N. R. B. 



Liverpool Marine Biology Committee. L.M.B.C. 

 Memoirs on Typical British Marine Plants and 

 Animals. Edited by Prof. W. A. Herdman. 

 xxiii. Tubifex. By G. C. Dixon. Pp. viii + 100 

 + 7 plates. (London: Williams and Norgate, 

 1915.) Price 3s. 6d. 

 Tuhifex rivulorum is a slender Oligochaete, not 

 more than two inches long, often found in large 

 numbers in the mud of rivers and streams, but 

 it occurs frequently also in brackish tidal waters, 

 and therefore a memoir on this worm is appro- 

 priately included in a series dealing with marine 

 animals. Of the aquatic Oligochaetes, Tubifex is 

 NO. 2400, VOL. 96] 



the type usually chosen for study in advanced 

 classes in this country. Accounts of the different 

 systems of organs have appeared in various zoolo- 

 gical publications, but for figures of the worm the 

 student has hitherto been dependent chiefly on 

 the memoirs of d'Udekem (1855) and Vejdovsky 

 (1884). Miss Dixon has revised and extended 

 the previous accounts, with the result that her 

 memoir gives a careful and reasonably full de- 

 scription of the structure of the worm, illustrated 

 by seven well-drawn plates, of which the first in 

 particular will be useful to the student. 



After a few general remarks on the habits of the 

 worm, an account is given of the external fea- 

 tures and of the various systems of organs, the 

 hermaphrodite reproductive apparatus being de- 

 scribed in considerable detail, almost one-half of 

 the memoir being devoted to this group of organs. 

 Of considerable interest is the discovery that 

 Tubifex possesses dimorphic spermatozoa. Both 

 kinds of spermatozoa are of the elongate type and 

 are tailed, but they differ in size and in the pro- 

 portions of their parts. In the ordinary spermato- 

 zoa the head forms about one-sixth of the total 

 length. The second type of sperm is about three 

 times as long as the ordinary one, and the head 

 forms about one-half the total length. 



A good account is given of the remarkable 

 spermatophores of Tubifex, which are moulded 

 into their characteristic form in the spermathecal 

 duct. 



The memoir concludes with a brief reference to 

 the parasites of Tubifex and a bibliography. 



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.] 



Distances at which Sounds of Heavy Gun-firing are 

 Heard. 



Referring to the correspondence on this subject, I 

 have been collecting information as to places at which 

 the sound of the firing in Belgium has been heard in 

 this country. 



I have undoubted records of its having been heard 

 at many places throughout the south-east of England 

 (all of them in Essex, Kent, Sussex, or Surrey), and 

 am giving the result of my inquiries in a paper to be 

 read before the Essex Field Club on October 30. 

 Here, at a distance of about 125 miles from Ypres 

 (taking that town for convenience, as a known centre), 

 I have heard firing quite unmistakably since the begin- 

 ning of the war — often all day, and for many days in 

 succession, and frequently at night too. 



So far as I have been able to ascertain, the greatest 

 distance from Ypres at which the firing has been 

 heard unmistakably is about 140 miles, though I have 

 a less satisfactory record up to 150 miles. No doubt, 

 however, it has been heard further in favourable con- 

 ditions. Observations seem to show that the direction 

 of the wind has less to do with the transmission of 

 the sound than certain atmospheric conditions, though 

 it is not easy to ascertain exactly what these condi- 

 tions are. 



