July 9, 1903J 



NA TURE 



221 



The work is primarily a contribution to systematic 

 dendrology, and cannot fail to be of interest and value 

 to the systematist. At the same time, the subject is of 

 considerable importance to the practical man, be he 

 nurseryman, forester, gardener, or landscape gardener. 

 In those professions winter operations often occur, in 

 which it is very important to be able to identify ac- 

 curately the different species. 



The special descriptions of the species dealt with in 

 the book, so far as they have been tested, have proved 

 to be quite accurate. There are a few misprints and 

 slips, which are, however, corrected in the errata at 

 the end of the book. There are one or two emenda- 

 tions still required, such as " Spartium junceum " in- 

 stead of " Sportium unceum," p. 22, line 3. Also in 

 the reference to the wood body of Fig. 31, given on p. 

 56, line 33, we would substitute " undermost layer " for 

 "uppermost layer." However, such slips will, no 

 doubt, disappear in a second edition, which we hope 

 to see this work reach, and in which the author will 

 be able to enhance the value of his work by the addi- 

 tion of still more species. 



La Tecnica delle Correnti Alternate. Vol. i. Parte 



qualitativa e descrittiva. By G. Sartori. Pp. xv + 



336; 260 illustrations. (Milano : Ulrico Hoepli, 

 1903.) Price L.8. 



The course of evening lectures read before a class of 

 artisans is here given in book form. Except for an 

 occasional algebraic expression, mathematics are 

 rigidly excluded, and yet the author tackles the most 

 complex phenomena of alternate currents, and dis- 

 cusses the behaviour of synchronous, asynchronous 

 and rotary-field motors, with their various starting 

 devices ; of rotary converters and their tendency to 

 hunt; of alternators running in parallel, and of wave 

 propagation in long lines. And he does this with so 

 much success that the usual treatment on the basis 

 of a sine wave- form compares unfavourably. A 

 mathematical treatment of the subject is practicable 

 only on the assumption of sine-waves, and the evil of 

 this is that students are apt to forget that in practice 

 the wave-form is rarely sinusoidal, and generally so 

 far removed from it that the theoretical deductions are 

 then valueless. To deal with alternate currents is far 

 harder without than with the use of sine waves, and 

 the author is to be congratulated on his success. The 

 book, in fact, is not an elementary manual, but an 

 up-to^ate treatise, its language suited to the artisan 

 and its substance to any student. 



Monographie des Cynipides d'Europe et d'Algdrie. 

 Par I'Abb^ J. J. Kieffer, Membre de la Socidt^ Ento- 

 mologique de France. Tome Second. Premier 

 Fascicule. Pp. 288; avec les planches 1^9. 

 (Paris : Hermann, 1903.) Price 16 francs. 



This is another instalment of the important series of 

 monographs forming part of the great work on 

 Hymenoptera inaugurated by the brothers Andr^. It 

 includes the portion of the parasitic Cynipidas com- 

 prised in the tribes Allotriinae, Euccelinae, and the 

 commencement of the Figitinae. The Allotriinae must 

 be regarded as very useful insects, for they feed 

 chiefly, if not exclusively, on Aphidas and Coccidae; 

 whether they ever attack other insects seems for the 

 present to be somewhat uncertain. The Euccelinae, 

 on the other hand, are parasites on the larvae and 

 pupae of Diptera, and sometimes on small Coleopterous 

 larvae, and the single recorded instance of their attack- 

 ing .Aphidae is considered by Kieffer to require con- 

 firmation, while the known larvae of the Figitinae are 

 parasitic on the larvae of Diptera, Coleoptera, and 

 Neuroptera. 



• NO. 1758, VOL. 68] 



The subject is treated in a similar manner to that 

 of the first volume, which we have recently noticed, 

 and several species are described as new. The former 

 standard of excellence i^ well kept up, both as regards 

 the text and plates. 



Spirals in Nature and Art. By Theodore Cook. Fp. 



xxi + 200. (London: John Murray, 1903.) Price 



7s. 6d. net. 

 That spiral curves, or, more strictly, helices, and 

 screw motions should play an important part both in 

 the natural world and in structures constructed by 

 human hands is a fact for which a mathematician can 

 easily suggest an explanation on general grounds. 

 Without professing to bring any extensive scientific 

 or technical knowledge to bear on the subject, Mr. 

 Cook has made a most interesting study of the resem- 

 blances between the spiral forms occurring in nature 

 and in art, and has produced a book the study of which 

 will be a delightful recreation to any class of reader. 

 Apart from the mere spiral form, Mr. Cook finds re- 

 markable resemblances between the structure and 

 sculpturing of certain staircases in France and those of 

 the shells of certain mollusca. It is certain that 

 Leonardo da Vinci studied shells, and that he was in 

 France about the time when these staircases were built, 

 and an obvious connection suggests itself. While the 

 author's study of the works of Leonardo da Vinci — 

 illustrated by copies of his drawings — is interesting, 

 the connection of Leonardo's studies of the flight of 

 birds with spiral curves strikes a reader as somewhat 

 doubtful. Even Pettigrew's figure-of-eight-shaped 

 curve, and the oval curve familiar to readers of 

 Marey's " Vol des Oiseaux," which represent, ac- 

 cording to modern views, the relative paths of points 

 on the wings of a wasp and a bird, can hardly be said 

 to produce a spiral curve when compounded with the 

 forward motion of the animal. 



Lois generales de I'Action des Diastases. Par Victor 



Henri. Pp. xi+129. (Paris: A. Hermann, 1903.) 

 After a general introduction on catalysis and a 

 classification of catalysers, the author gives a historical 

 account of the work already done on the action of 

 diastases. Then follows a description of his own re- 

 searches on the action of invertase on cane-sugar, 

 together with the theoretical deduction of a formula 

 which represents with considerable accuracy the actual 

 course of the reaction under varying conditions of 

 concentration. The book concludes with two short 

 chapters on the action of emulsin on salicin, and of 

 amylase on starch. The author shows an intimate 

 acquaintance with the mode of application of the laws 

 governing the velocity of chemical action, and has 

 been successful in selecting appropriate experiments to 

 solve the problem with which he was confronted. 



Sylviculture. By Albert Fron. Pp. xii + 563. (Paris: 



J. B. Baillifere et Fils, 1903.) Price 5 francs. 

 This is one of the volumes of the useful " Encyclo- 

 pddie Agricole " which is appearing in France under 

 the auspices of a " Reunion d'lng^nieurs agronomes. " 

 It deals succinctly with the methods of cultivation of 

 woods for commercial purposes, gives an account of 

 the chief timber trees, and also deals with the products 

 of forests and the manner of their conversion, in 

 accordance with French practice. 



The book has no special feature. It is, well adapted 

 to the requirements of students of the " Ecole Nation- 

 ale d 'Agriculture," for whom it is intended, and 

 forms a useful addition to its series without replacing 

 the larger text-books on the forestry of France — such 

 as those of Boppe. 



