146 



NA TURE 



[December 17, 1 1 



use of " Disconanthe" and " Siphonanthe," in place of 

 " Disconanthas" and " Siphonanthae," are astonishing, 

 when we note that the translator is M. A. of the University 

 which refuses to inquire whether "compulsory Greek" is 

 useful or not. 



A very different work from Prof Lang's is the treatise 

 on the embryology of the Invertebrata by Drs. Korschelt 

 and Heider, of the University of Berlin, of which an 

 English translation is in preparation. Two parts of this 

 admirable book have appeared, containing 900 pages and 

 more than 500 woodcuts, dealing with the embryology of 

 the Porifera, Cnidaria, Ctenophora, Platyhelmia, Ortho- 

 nectidae, Dicyemidae, Nemertina, Nemathelminthes, 

 Acanthocephali, Rotatoria, Annelida (including Echiurids 

 and Leeches herein), Sipunculidae, Chaetognatha, Entero- 

 pneusta, Echinoderma, and the Arthropoda. The various 

 classes of the last-named phylum occupy two-thirds of 

 the work at present issued. There remain still to be 

 dealt with the Mollusca, the Bryozoa, and the Tunicata. 



The best idea which can be given of the scope and 

 value of this work is obtained when we compare it with 

 Frank Balfour's treatise on comparative embryology. It 

 is not too much to say that it is the most valuable 

 text-book for the zoological student which has appeared 

 since Balfour's book, and is a worthy successor to it. The 

 mass of literature, vast as it was ten years ago, has 

 increased enormously in the interval. Drs. Korschelt 

 and Heider have carefully gone over it all ; and not only 

 that, but they accurately and clearly give each author's 

 contribution to the subject in hand, citing authority for 

 every statement made, so that the student can go to the 

 original treatises for fuller detail. I do not know of any 

 scientific treatise which shows so clearly the authors' 

 desire to do justice to every fellow-worker of whatever 

 nationality, and to produce a work which shall be a com- 

 plete and trustworthy guide to the recent literature of a 

 prodigiously prolific subject. Very often the authors 

 abstain from offering a decided opinion upon a matter 

 where the observations made have led previous writers 

 to diverse conclusions : such cases are those in which the 

 facts are incompletely observed and obviously require 

 renewed investigation. But where the observed facts on 

 one side or the other are of a decisive character, the 

 authors, after giving both sides in detail, exercise a 

 judicial function. 



The book deals not only with the earlier but also with 

 the later stages of development, and not merely with the 

 facts of embryology, but with the conclusions as to the 

 affinities of groups, which are so severely tested by 

 the progress of embryological inquiry. 



It is not possible to particularize in regard to such a 

 work as this, but I have been struck by the very full way 

 in which the morphology of the Crustacea, and each 

 succeeding class of Arthropods, has been dealt with in j 

 every respect in which embryology throws light upon it. 

 A very fully illustrated chapter gives a complete and im- 

 partial account of the researches of Sedgwick, Sheldon, 

 and Kennell on the development of different species of 

 Peripatus. The question as to the relationship of the 

 Arachnida to Limulus and the Eurypterines, alluded to 

 above, is fully treated by Drs. Korschelt and Heider. They 

 summarize the arguments with clearness, and state and J 

 NO. I 155, VOL. 45] 



weigh fairly nearly every fact which has been adduced in 

 favour of the association of Limulus and the Eurypterines 

 with the Arachnida. Their conclusion is as widely 

 different from Lang's as is their method of discussion. 



There can be no doubt that we have in this new treatise 

 on comparative embryology one of those invaluable, 

 indispensable works for the production of which authors 

 receive the gratitude and esteem of their fellow-workers 

 in all lands. It is a truly first-rate book. 



E. Ray Lankester. 



MODERN ARTILLERY. 

 The Artillery of the Future and the New Powders. By 

 James Atkinson Longridge, M.I.C.E. (London: E. 

 and F. N. Spon, 1891.) 



MR. LONGRIDGE keeps pegging away at his 

 favourite subject, which he originally brought for- 

 ward, now more than thirty years ago, in the Proceedings 

 of the Institution of Civil Engineers. 



His valuable ideas are at length receiving recognition, 

 and his principle of strengthening guns, by layers of wire 

 wound with appropriate initial tension, is now largely 

 employed in the construction of modern ordnance. 



The chief object of the present book is to point out 

 that the fullest application of his principle of wire 

 strengthening permits of the use of much higher powder 

 pressures than are considered admissible in Government 

 circles ; and that thereby guns may be much shortened 

 and reduced in weight, while at the same time the full 

 power of the most modern high explosives can be utilized. 



This is to a great extent a re.turn on the steps which 

 have guided our gun designers in recent years ; their chief 

 object being, to reduce initial pressure as much as pos- 

 sible, say down to 17 tons per square inch, and to get 

 the full power out of the powder by a great increase in the 

 length of bore, up to 40 and even 50 calibres in length in 

 guns of large size. 



Mr. Longridge is fully acquainted with all the valuable 

 and original work in gunnery science which has been 

 developed of late years in France by Sarrau, Veille, and 

 Sebert ; and analyzes carefully in chapters ii. and iii. 

 the various experimental methods and empirical formulas 

 in use for the measurement of powder pressure in the bore 

 of a gun. 



In chapter iii. he attempts a theoretical explanation 

 and formula for maximum pressure and total energy, but 

 his investigation rests upon an assumption of the adiabatic 

 law ; and the mathematical treatment is not presented 

 in an inviting or elegant form. Considering the unex- 

 plained chemical combinations which affect the rate of 

 combustion of the modern smokeless powders, this 

 mathematical assumption can only roughly account for 

 an average performance, and leaves unexplained the 

 violent abnormal effects sometimes experienced and 

 shown in General Wardell's curves, to guard against 

 which the gunmaker has to exercise a vigilant caution. 



General Brackenbury is quoted as calling gunpowder 

 the Spirit of Artillery, and in his official capacity. Super- 

 intendent of the Royal Gunpowder Factory, as a maker 

 of gunpowder, saying metaphorically, " How sad the body 

 is so weak " in preference to " What a pity the spirit is so 

 strong." 



