52 



NATURE 



[May 



L903 



years old, the huge iron girders at Puri, the iron- 

 roofed temple porch at Kanurac, and other relics which 

 show the ancient familiarity of the Hindus with this 

 metal. In the fourteenth century brass and bell-metal 

 were stated to be alloys, and zinc, copper and tin to be 

 metals. The manufacture of gold jewellery is also of 

 great antiquity in India. 



Dr. Ray has ably carried out his task of proving 

 that the ancient lore of the Hindus was far in advance 

 of that of the rest of the world, China excepted. The 

 reader who is unversed in Sanskrit may perhaps be 

 pardoned if he sometimes loses himself for a moment 

 in the maze of Hindu names, and it will be well if his 

 *' discerning faculty is nimble and agile, and can 

 suddenly surround a proposition." A glossary would 

 be useful, but could scarcely add to the interest of the 

 volume. The second volume, promised when Dr. Ray 

 has examined further manuscripts, will be welcome. 



T. K. R. 



OVR BOOK SHELF. 



The Soil : an Introduction to the Scientific Study of 

 the Growth of Crops. By A. D. Hall, M.A. Pp. 

 xiii + 286. (London : J. Murray, 1903.) Price 

 35. 6d. 



When one who has been for many years both a teacher 

 and an investigator commits to paper the facts and 

 Ideas which have formed the substance of his later 

 courses of instruction, we expect a very useful book, 

 and in the present Instance we are certainly not dis- 

 appointed. The book before us takes a wide scope ; 

 it deals with the origin of soils, their physical proper- 

 ties, their chemical properties and composition, 

 methods of analysis, the living organisms within the 

 soil, the causes of fertility and sterility, soil types and 

 the natural flora belonging to each. The book is 

 primarily Intended for college students. Owing to its 

 wide scope It does not attempt to treat any part of the 

 subject In an exhaustive manner ; It possesses, how- 

 ever, the great merits of originality and suggestlve- 

 ness, virtues which are not always to be found in the 

 formal text-book. A prominent feature of the work 

 is the introduction of the results of investigations 

 carried on by the author while principal of the Agri- 

 cultural College at Wye. English books on scientific 

 agriculture have hitherto been so necessarily filled with 

 descriptions of foreign researches that any results 

 obtained under English conditions have an exceptional 

 value, and appeal to the farmer in a special manner. 



In a work dealing with so many subjects, there are 

 naturally some points open to criticism. The author 

 seems to hesitate in attributing some of the physical 

 properties of soil constituents to their colloid nature, 

 and thus leaves unexplained the enormous amount of 

 hygroscopic water held by humic matter. The indigo 

 method of determining nitrates is mentioned as one 

 that may be used for determining nitrates in soil ex- 

 tracts; the method is, in fact, unsuitable for this pur- 

 pose, as it gives results much below the truth owing 

 to the presence of organic matter. Nitrification is 

 occasionally spoken of as a kind of " fermentation "; 

 objection may surely be taken to this description. 

 Fermentation is a word of wide meaning, but it surely 

 should not include the oxidation of inorganic matter 

 by a living organism. The chapter dealing with the 

 power of soils to retain various bases and acids is full 

 of interest, yet the theory is incompletely stated, the 

 results of the German, French, and some English 



NO. 1 75 I, VOL. 68] 



investigations on the subject being unnoticed. TIk 

 laws governing the diffusion of salts, and the results 

 of their molecular diffusion in a moist soil, are also 

 not noticed. The cause of the sterility of alkali lands, 

 and their proper treatment, are, however, well dis- 

 cussed, and many excellent illustrations of the sub- 

 ject are introduced from the experience gained in 

 Egypt. 



In a book dealing with many details some slips will 

 Inevitably occur; the most important one In the present 

 case is that King's determinations of nitrates in fallow- 

 soil appear as cTetermlnations of nitrogen as nitrates ; 

 the quantity of nitrates present is thus unintentionally 

 much exaggerated. 



The concluding chapters on fertility and soil typ< 

 exhibit most fully the thoroughly practical characti > 

 of the author's teaching, and will be much valued b> 

 many readers. The book is sure to meet with a 

 favourable reception. R. W. 



Electrical Problems for Engineering Students. By 

 W. L. Hooper, Ph.D., and R. T. Wells, M.S. Pp. 

 v+ 170. (Boston and London : Ginn and Co., 1902.) 

 Price 6^. 



This is a collection of numerical and mathematical 

 exercises In electrical engineering, starting from the 

 most elementary beginning and ending in the more 

 difificult problems presented by the design and working 

 of direct and alternating current dynamos and motors. 

 The exercises have been tested by the practical experi- 

 ence of the authors at Tuft's College, Mass., and are 

 such as would form a useful accompaniment to a two 

 or three years' lecture and practical course. A dis- 

 tinctly good feature of the book Is the number of ex- 

 amples requiring graphical solutions, which cannot 

 fail to impress upon the student the advantages gained 

 by plotting curves. It is always an objection to 

 exercises of this sort that they tend too much to the 

 purely arithmetical and academic side of the subject; 

 thus, many of the problems on subjects which are 

 treated only in an elementary manner in this book are 

 little better than arithmetic sums. For example, In 

 the twelfth chapter, on electrochemistry, there are 

 eleven problems, which are all practically simple pro- 

 portion sums, and we doubt if the student would gain 

 much more by solving them than he would by solving 

 an equal number of problems on, say, the number of 

 able-bodied men and boys required to till a field. But, 

 If the book be used with discretion, these drawbacks 

 will be lessened, and provided the student Is taught In 

 other ways to think about and really understand his 

 subject, these exercises will serve to give him a facility 

 In attacking numerical problems as they arise. The 

 book should prove a useful aid to students and teachers 

 of electrical engineering. M. S. 



Open-Air Studies in Bird Life; Sketches of British 

 Birds in their Haunts. By C. Dixon. Pp. xii + 280; 

 illustrated. (London : GrifTin and Co., Ltd., 1903.) 

 Price 75. 6d. 

 Mr. Dixon appears to consider that the appetite of 

 the British public for books on the birds of their 

 own Islands Is insatiable, and as he seems to find 

 a publisher for all his works on this subject, he is 

 perhaps justified in this opinion. In the present In- 

 stance the subject is treated from a standpoint some- 

 what different from the one usually adopted, the birds 

 being described in connection with their environment 

 or "station," instead of systematically. Although 

 this mode of treatment necessarily involves a certain 

 amount of repetition (as in the case of the sparrow 

 and the lapwing), it permits the descriptive side of the 

 subject to be relegated somewhat to the background, 



