246 



NATURE 



[July 13, 1893 



are here and there rather poor, and a higher general 

 standard in this respect might easily have been attained. 



After a general analysis, so to speak, of dynamos, in 

 which armatures, magnets, &c., are discussed, we come 

 to matters relating to the action of dynamos, such as 

 series, shunt, and compound winding, and sparl<ing and 

 angle of lead of brushes. Then follow descriptions of 

 typical hiachines, illustrated by folding sheets, and the 

 book closes with chajDters on Dynamo-Designing, and 

 the Working and the Management of Dynamos. 



We should have liked to have seen dynamo-testing 

 worked out more fully, and a separate chapter on this 

 important subject might easily have been given without 

 burdening the book with matter properly belonging to 

 works on general electrical measurements. 



Considering the compass of the book — 520 small Svo 

 pages — the authors have succeeded in placing before their 

 readers a very great amount of valuable information, well 

 arranged and clearly expressed, and their work will no 

 doubt be appreciated by students and workers in practical 

 electricity. A. Gr.\y. 



OUR BOOK SHELF. 



Modern Microscopy : a Hand-book for Beginners. In 

 two parts. I. " The Microscope, and Instructions for 

 its Use.'' By M. J. Cross. 2. " Microscopic Objects : 

 how Prepared and Mounted." By INIartin J. Cole. 

 (London: Baillifere, Tindall, and Co.t, 1893.) 



This book, although only e.xtending to 104 pages, is what 

 it professes to be, and will prove thoroughly useful to 

 beginners. The authors understand practically their 

 respective subjects, and this has given the capacity, never 

 otherwise possessed, to tell the beginner accurately and 

 efficiently what it is needful for him at the outset to know. 



It is highly to be commended that they have not 

 rendered their pages incompetent by any pretence at an 

 introduction to the optics of the instrument, or concerned 

 themselves with any attempt at e.xposition of modern 

 optical theory. They have done what affords a more 

 genuine evidence of their appreciation of the importance 

 of these subjects, having presented the results of the study 

 of them in a practical forai to the beginner, so that although 

 his earlier efforts are not complicated with mathematical 

 demonstrations and theory, he is nevertheless taught to 

 work, on the highest results reached through these, so far 

 atjeast as they apply to his initial endeavours. 



The danger of extremely elementary books on 

 microscopy is shallowness. They have often been a mere 

 catalogue of two or three chosen instruments, with brief 

 accounts of the apparatus affected by the author, and 

 descriptions of pretty or pleasing objects. The former 

 part of this book is much more than this; it gives the 

 results of a practical knowledge of how to employ the 

 instrument in such a way as to attain the finest results ; 

 always remembering that it is beginners that are receiving 

 the instruction. 



There are some thoroughly sensible things said on the 

 microscope-stand. We may differ slightly from some of 

 these, but they are written with a knovvledge of the sub- 

 ject, and those who follow them will not greatly err. 



We can commend also the chapter on " Optical 

 Construction." It is brief, but puts to the beginner 

 exactly what he requires to know. The pages on 

 "Illuminating Apparatus" are specially commendable 

 because thoroughly experimental. In fact, the fifty-five 

 pages devoted to modern microscopy will be a boon to 

 every one of the many who are every year " beginning" 

 with the use of the microscope. 



But the practical character of the book is seen even 

 more clearly in the second part of it, by Mr. Martin Cole. 



NO. 1237, VOL. 48] 



He at once introduces the tyro to the art of preparing and 



mounting his own objects Here again it is not a mere 

 repetition of what has been obtained from other sources 

 that is presented, but Mr. Cole's long experience as a 

 mounter is given to the reader unostentatiously and wiilj 

 pleasant and useful brevity. 



There are some who, glancing at this little treatise, 

 will at once conclude that the thirty-six pages devote^ 

 to the subject must leave it inefficiently treated even for 

 beginners. We advise such to read the pages; and after 

 some years of practice in most of the departments of 

 mounting referred to and explained, we can only say that 

 they present in a brief but a very efficient manner the 

 facts required to enable the earliest efforts of an earnest 

 amateur to become so successful as almost certainly to 

 secure his interest in the subject, and cause him to in- 

 telligently pursue his pleasure and instruction, if not to 

 aim at scientific work directed by more exhaustive 

 treatises. W. H. Dallinger. 



Lectures on Sanitary Law. By A. Wynter Blyth, 

 M.R.C.S., L.S.A. (Macmillan and Co. 1893.) 



This work presents a general view of the powers and 

 duties of Local Authorities in relation to public healtb, 

 and since the material has been compiled by one who, 

 while he is a prominent sanitarian is also a barrister-at- 

 law, the fact that the work is good and trustworthy, aad 

 leaves but little to be desired, goes without saying. The 

 only point upon which there is any scope for adverse 

 criticism is that the review of sanitary legislation appears 

 to be, in places, a little too cursory, and in conse- 

 quence some important material is a trifle too hurriedly 

 passed over. To indicate one such instance : — '! here 

 is some important material contained in the Dairies, 

 Cowsheds, and Milkshops Orders of 18S5 and 1886 

 which is not given, and with which the health-offi:er is 

 directly concerned. Sections 10, 11, and 12 of the 1885 

 Order are omitted ; and no one will question thei' right 

 to be fully included within any serviceable abstract of 

 the ( rder, since they deal specifically with certain wdl 

 recognised sources of contamination, against which itis 

 necessary to guard the milk in those places where it is 

 stored or kept for sale. 



Nothing need be more inclusive or better expressed 

 than the majority of the work, and when in one cr two 

 places the information is a little more extended, and the 

 statutes specially dealing with the inspection and examin- 

 ation of food (which are now given 171 extenso in the 

 appendix) are incorporated in, say, another two chapters, 

 the book will be rendered even more acceptable than it is 

 at present to those desirous of obtaining in a readable and 

 concise form a good knowledge of sanitary legislation. 



The scope of the book embraces the entire range of 

 public health legislation, and the volume is largely an 

 embodiment of a series of lectures which have frequently 

 been given by the author. The first chapter treatsof the 

 constitution of Sanitary Districts and Authorities, and in- 

 cludes the definitions of certain terms employed in the 

 Sanitary Acts. Lecture ii. deals with the statutory pro- 

 visions regarding nuisances ; and the next three lectures 

 are concerned with the legal aspect of sewerage and 

 drainage, water-supply and sanitary appliances ; regu- 

 lations and bye-laws ; port sanitary law, canal boats, 

 Metropolitan sanitary law, the Housing of the Working 

 Classes Act, 1890, are all dealt with in subsequent 

 chapters ; and the statutory provisions which deal with 

 the prevention of disease are particularly well and clearly 

 mapped out in Lectures vi. and vii. The book comprises 

 nearly 300 well-printed pages, and it is neatly and 

 serviceably bound. 



The author must be congratulated upon having pre- 

 sented a rather heavy and unattractive subject in the most 

 concise and readable form — consistent with general use- 

 fulness — of any in which it has hitherto appeared. 



