200 



NATURE 



[August i8, 1910 



no department of the science of mind does there 

 prevail greater confusion and uncertainty than in that 

 of Vohtion." 



In the present voluihe Prof. Ach continues the 

 records and resuhs of his prolonged investigation into 

 will-psychology ; the former instalment being his 1905 

 treatise, " Uber die VVillenstatigkeit und das Denken." 

 An account is given of the experimental method em- 

 ployed, which is largely a combination of those of 

 Ebbinghaus and G. E. Miiller. He employed eighteen 

 subjects who were practised on reproduction of 

 syllables, rhymes, and the like components of methods 

 well known in laboratories. 



As his main result, the author claims to have shown 

 that the act of will is a specific psychic experience. 

 The positive phenomenal characteristics of a primary 

 volition are (i) the perceptive moment — sensations of 

 tension ; (2) the objective moment — ideas of reference 

 and end, purpose, and means; (3) the actual moment — 

 the acoustic — kinesthetic, " I will actually " ; (4) con- 

 ditional moment — consciousness of effort. Of these 

 the chief is (3), and he explains why it has hitherto 

 been so often ignored. None of these moments, of 

 -course, is independent ; they are sides of one fact. 

 Great spectacular results are not expected from ths 

 ininute laboriousness of experiments like these; but 

 they are latent, and, as Weber's Law, for instance, 

 has done, will emerge in due time. Vet light is 

 thrown on a score of "little problems." Not the least 

 interesting, and the most detailed, discussion is that 

 on weakness of will. A close study of this chapter in 

 connection with the tabulated results of the investi- 

 •gation which occupy the first half of the volume 

 would be a fruitful piece of book-work for the learner. 

 Prof. Ach rightly censures the use of such examples, 

 as the famous "How we get up in the morning" of 

 Prof. James, for illustrating the mechanism of voli- 

 tion. Trained or habituated will is precisely that 

 form of the process which is least original. Here, by 

 the way, in the relation between habit and will — a 

 relation of practical, no less than theoretical, import- 

 ance — is a fruitful field for investigation. Another 

 fruitful area is the connection between will' and tem- 

 perament. Prof. Ach ends his volume with a few 

 suggestive pages on this subject. 



The material supplied by the author's ir.vestigation 

 is probably rich enough to yield further results if 

 re-studied. So far, the author has been led towards a 

 reaction against the prevailing view of will-processes. 

 Without doubt this and similar work is clearing the 

 ground for a new psvchologv, both of feeling and of 

 will. 



A. BOOK OF CHARACTERISTIC FOSSILS. 

 Leitfossilien : ein Hilfsbitch zitm Bestimmen von 

 Vcrsteinerungen bei geologischcn Arbeiten in der 

 Saminlung und im Fclde. Lief. L : Kambrium und 

 Silur. By Prof. Georg Giirich. Pj). 95. (Berlin : 

 Gebriider Borntraeger, 1908.) 

 pROF. GEORG GURICH has prepared a well- 

 ^ illustrated handbook of characteristic fossils 

 which is now in course of publication in eight parts. 

 It i>> intended for elementary students and amateurs 

 i\0. 2129, VOL. 84] 



who are occupied with geological work and desire an 

 exact knowledge of those fossils which are of special 

 value in determining the relative ages of rock-forma- 

 tions. It is not a treatise on common fossils, and 

 those who seek in it an account of so familiar a 

 brachiopod as Atrypa reticularis, for example, will be 

 disappointed ; but it deals with those species and 

 genera which, whether common or not, happen to be 

 restricted in their geological range, and are thus of 

 service as unerring time-markers. The fossils of each 

 successive period are taken in order, beginning with 

 the earliest; and the twenty-eight plates included in 

 the first part of the book are devoted to those of the 

 Cambrian and Silurian formations. The figures are 

 not original, but judiciously selected from standard 

 works, and all are beautifully reproduced by a half- 

 tone process. The accompanying text consists chiefly 

 of brief definitions of the various groups, families, 

 genera, and species, in systematic order under each 

 geological formation. There are also useful synoptical 

 tables, both of the formations themselves in different 

 parts of the world and of the fossil species which are 

 characteristic of eacli special stage. Occasional te.xt- 

 figures are added to explain structural features and 

 the more important anatomical terms emploj'ed. In 

 the first part, the figures illustrating the structure of 

 trilobites and graptolites are especially good. 



Dr. Giirich docs not recognise an Ordovician system, 

 but classifies the formations from the Tremadoc to the 

 Caradoc inclusive as Lower Silurian. His work is 

 also unusual among stratigraphical handbooks in 

 paying special attention to fossil plants and vertebrates 

 when they can reasonably be claimed as of value. 

 His first reference to vertebrates, however, in the 

 Upper Silurian is unfortunate, for it takes no account 

 of Dr. Traquair's important discoveries, and repeats 

 an old error in supposing that the shagreen named 

 Thelodus belongs to the same fish as the fin-spines 

 named Onchus. In view of present rapid progress 

 and specialisation this oversight is not surprising, and 

 Dr. Giirich is to be congratulated op having made an 

 excellent beginning of a useful r,;id trustworthy 

 student's manual. 



METALLOGRAPHY. 

 Metallographie : Ein ausfUhrliches Lehr- und Hand- 

 buch der Konstitution, und der physikalischen, 

 chemischen und technischen Eigenschafien der 

 Metalle und metallischen Legierungen. Erster 

 Band, Die Konstitution, Hefts, i. and ii. By Dr. W. 

 Guertler. (Berlin : Gebriider Borntraeger, 1909.) 



I'^HE number of investigations in metallography 

 published up to 1902 amounted to about one 

 thousand, but to-day reaches three times that number. 

 This fact alone makes the appearance of a complete 

 text-book on the subject most welcome. 



The work is appearing in parts, the first two of 

 which consist each of eighty imperial octavo pages, 

 and it is expected that seven or eight more similar 

 instalments will complete the first volume, which is 

 devoted to the constitution of metallic alloys. A 

 second volume, dealing with the physical and chemical 

 properties of the alloys and with their technical appli- 

 cations is to follow. 



