1 7 8 



NATURE 



[August io, 191 i 



meaning of the term, determination of solubility, and 

 the plotting of curves is explained. The sub- 

 ject is taken up again at the beginning of 

 part ii., when equilibrium between solids and liquids 

 is discussed, and such topics as supersaturation and 

 eutectics are considered. Again, the effect of the elec- 

 tric current in effecting chemical change described in 

 part i. serves as an introdution to the theory of ionic 

 dissociation presented in part ii. In this way there is 

 little or no overlapping, and the subjects are sys- 

 tematically developed. Also, a zealous beginner who 

 wishes to learn something more of a subject may, if 

 he chooses, turn to part ii., and satisfy his curiosity, 

 although unfortunately no reference is given in the 

 text to the continuation in the advanced section. The 

 possible disadvantage of such treatment is that it 

 limits the scope of part ii. through want of space, and 

 consequently restricts the range of some of the sub- 

 jects which might otherwise have been expanded with 

 advantage. This criticism may, of course, be met by 

 the different view of the authors as to the standard 

 of knowledge demanded for the pass degree. 



Fulling- this point on one side, the book, we feel 

 sure, will commend itself to teachers and students 

 by its logical arrangement, clear descriptions, excellent 

 illustrations (with the exception of Fig. 51), and 

 convenient size. It may also be pointed out that, un- 

 like some of its predecessors, it is not overloaded with 

 facts. There are some omissions in the index. Thus 

 " the law or rule of Le Chatelier " is twice referred 

 to in the text, but is left out of the index, and so is 

 "vapour pressure." Charcoal stoves (p. 121) are said 

 to yield carbon monoxide, which is true enough, but 

 so do coke stoves, which are much more common, 

 at least in this country, and a frequent source of 

 danger. 



(5) Every teacher sooner or later will probably con- 

 sider that his peculiar experience will afford him 

 special advantages for producing a book on practical 

 chemistry. Indeed, it seems a natural and proper 

 feeling in anyone devoted to the subject. Whether 

 the results obtained by different methods are essentially 

 different is another question. One is inclined to think 

 that it is the teacher rather than the book that counts 

 in the long run. Here at least is a book produced by 

 two teachers whose hearts are in their work, and 

 who possess the additional advantage of being "un- 

 trammelled bv examination requirements of any kind." 

 Through their laboratory 300 boys pass weeklv and 

 are instructed by the methods described in their book. 

 This, along with the traditions of the school, on its 

 scientific side, are strong recommendations in them- 

 selves, and are further emphasised by a study of the 

 character and arrangement of the exercises. The 

 latter are clearly described and illustrated, and follow 

 in a natural and logical sequence. The apparatus is 

 simple and easily made and set up, and the number 

 of quantitative operations sufficient to ensure exact 

 manipulation. One feels that school chemistry is here 

 dignified as a rational study rather than imposed as 

 a compulsory acquirement of " the dirty part of 

 physics." It is a book that may be warmly recom- 

 mended for use in any well-equipped school laboratory. 



J. B. C. 

 J 180, VOL. 87] 



OUR BOOK SHELF. 

 Factor-table for the First Ten Millions containing the 

 Smallest 1' actor of every Number not Divisible bv 

 2 . 3> 5> ° r 7 between the Limits o and 10,017,000. 

 By Derrick N. Lchmer. Pp. xvi + 476. (Washing- 

 ton : Carnegie Institution, 1909.) 

 The condensation of a ten-million factor-table into 

 a single volume of fewer than 500 pages is a re- 

 markable feat, and it is interesting to learn how it 

 has been done. The author's manuscript was first 



typewritten in duplicate, and these sheets, after cc - 



tion, were photographed on glass. The photographs 

 were inspected and corrected and then transferred to I 

 zinc plates, so that no movable types were employed 

 in the printing. It is difficult to imagine a more 

 effective way of preventing errors after passing for 

 the press. The result is very compact and quite 

 legible; auxiliary tables are provided for finding the 

 proper entries in the main table : these may, however. 

 be dispensed with, if desired. Multiples of 2, 3, 5, 7 

 are omitted, so the arrangement is really that of 

 residues prime to 210. 



There is an interesting introduction, giving accounts 

 of previous tables and the method of sifting out suc- 

 cessive primes ; it also contains a valuable list of 

 errors in former tables. More interesting still is th» 

 account of the MS. tables by Kulik, preserved by the 

 Vienna Royal Academy. They are in six volumes, and 

 profess to give the smallest factors of all numbers not 

 divisible by 2, 3, or 5 up to a hundred millions. Kulik 

 uses a special notation, and, judging by his tenth 

 million, his work is not very trustworthy (not nearly 

 so good as Dase's, for example); but the existence of 

 such an enormous calculation by one man is very 

 remarkable. He appears to have worked at it for 

 twenty years. 



The author makes due acknowledgments for help 

 received; one of these is of international interest. The 

 funds for preparing the manuscript and publishing the 

 tables were furnished by the Carnegie Institution of 

 Washington. Such a contribution to abstract science 

 deserves cordial recognition and gratitude; and we 

 hope that colleges that can afford to do so will 

 promptly buy copies of this work. For although a 

 factor-table is not often wanted, ii i< in certain 

 circumstances indispensable, and it is very convenient 

 tn have one at a reasonable distance that can be 

 personally consulted. G. B. M. 



Didaktische Handbiicher fur den realistischen Unter- 

 richt an hoheren Schulen. Edited bv Prof. A. 

 Hdfler and Prof. F. Poske. Band vii., Didaktik 

 des botanischen Unterrichts. By Prof. B. Lands- 

 berg. Pp. xiii + 303. (Leipzig and Berlin : B. G. 

 Teubner, 1910.) Price 8 marks. 

 A consideration of the title gives rise to the reflec- 

 tion, how far this series of didactic handbooks owe- 

 its inception to the German educational system con- 

 trolled to a great extent by official regulations; yet 

 tiie present volume affords proof that changes in 

 teaching methods can be, and are, effected by indi- 

 vidual efforts. The main idea, advocated by Prof. 

 I.indenberg, of instruction based on practical observa- 

 tion and experiment, has already received general 

 approval, but the proposed sequence of procedure, 

 explicitly scheduled under three stages, does not 

 appear to be entirelv realisable or acceptable. During 

 the first stage, that extends over two years, tin- 

 governing principle, expressed briefly, is to induce the 

 study of single organisms in their environment with 

 regard to form and working of the different members 

 The collation of individuals into groups, both ecological 

 and classificatory, is relegated to the second stage, 

 when it is proposed that a course of anatomy and 



