September 26, 1884. 



SCIENCE 



311 



than by a simple collation of vocabularies — 

 aided, where practicable, b} T grammatical com- 

 parisons — to ascertain the relationship of the 

 various idioms, and to reduce them into the fami- 

 lies to which the}' belong. It is probable enough 

 that some isolated languages would be found , like 

 the Basque in Europe and the Khasi in farther 

 India, whose kinship could not at present be 

 determined ; and, of course, the ' language- 

 map ' would show many vacancies : but these 

 are imperfections which belong to the earlier 

 stages of all investigations. In spite of such 

 drawbacks, a scientific classification could have 

 been made, which would have gone far to bring 

 this linguistic chaos into order, and would have 

 thrown a flood of light upon African ethnology. 

 But while regretting these deficiencies in Mr. 

 Cust's work, we must be thankful for what we 

 have gained from him, which is not a little. 

 In these two A'olumes we have a clear and read- 

 able account of the present state of African 

 philology, and a complete list of the tribes and 

 languages of the continent, so far as they are 

 now known, with interesting details concern- 

 ing many of them. The names of all the 

 authors who have written on the subject, and 

 the titles of their productions, are given with 

 commendable fulness and precision. • The work 

 displays great industry and conscientious ac- 

 curac} T . The extensive ' language-map,' which 

 has evidently been prepared with much care, 

 aids materially in illustrating the text, and is 

 in itself a most valuable contribution to philo- 

 logical science. In spite of the defects which 

 have been indicated, Mr. Cust's treatise must 

 be pronounced to be by far the best work which 

 we possess on the subject to which it is de- 

 voted. Scholars who pursue this important 

 branch of linguistic study will find in these 

 attractive volumes a highly useful, and indeed 

 almost indispensable, guide. H. H. 



MINOR BOOK NOTICES. 



The development theory : a brief statement for general 

 readers. By Joseph Y. Bergen, jun., and 

 Fanny D. Bergen. Boston, Lee $f Shepard, 

 1884. 7 + 240 p. 24°. 



No better evidence of the present general 

 interest in biology could be wanted than is 

 afforded by the growing demand for popular 

 books on evolution. The latest of these is a 

 little treatise of two hundred and forty pages, 

 by Mr. and Mrs. Bergen, in which, to be sure, 

 not much is original, except the form in which 

 the facts are presented, and a few of the exam- 

 ples cited, as the authors confess ; but a read- 



ing of their book shows that they have given 

 a good deal of thought to the presentation of 

 the chief arguments upon which the modern 

 development theory rests, with so few techni- 

 calities as to render it comprehensible to even 

 young readers. With so many books of a 

 similar character already in circulation, only 

 the test of time can show whether this latest 

 one meets, as the authors intended, a real need. 

 So far as one not wholly unfamiliar with the 

 subject can judge, the story is well and simply 

 told. 



Calcul des temps de pose et tables photometriques. 

 Par Leon Vidal. Paris, Gauthier- Villars, 1884. 

 114 p. 16°. 



This little book is made up very largely of 

 tables, whose object is to enable the photog- 

 rapher, when supplied with a particular form 

 of photometer, to give the correct exposure 

 to his plate under all circumstances. The 

 book is apparently written largely for ama- 

 teurs in landscape-photography ; but whether 

 the}^ will in general be willing to trouble them- 

 selves to procure such a photometer, and carry 

 round the tables with them to consult whenever 

 they wish to take a picture, in preference to 

 relying on their judgment, is perhaps ques- 

 tionable. The photometer employed is similar 

 to that used by carbon-printers, depending on 

 the exposure of sensitized silver-paper, and the 

 noting of the tint obtained after a definite time. 

 The author refers to the application of the in- 

 strument to the case of enlargement,' where it 

 would seem to be more useful than when tak- 

 ing the original negative. There is one serious 

 objection to its employment for the latter pur- 

 pose, however, which our author seems to have 

 overlooked. This is, that the exposure for a 

 given landscape does not depend wholly on 

 the total amount of light coming from it. If 

 • the background is the important portion, a 

 certain definite exposure will be given. If, on 

 the other hand, it is the foreground that is of 

 interest, the same view ma}^ require two or 

 even three times the exposure under the same 

 conditions. 



Leiddraad bij het onderwijzen en anleeren der dier- 

 kunde. Door Dr. Julius MacLeod. Alge- 

 meene dierkunde. Met eene titelplaat en 61 

 door den schrijver gegraaverde figuren. Gent, 

 1883. 151 p. 12°. 



The author of this little school-book has 

 written it in the Dutch language, in the patriotic 

 belief that dierkunde, or zoology, may be 

 taught in that tongue, which can supply all 

 the necessary terms. The volume is really a 



