SCIENCE. 



[N. S. Vol. XII. No. 300. 



lished in the Philosophical Transactions, Part II., 

 1879. Unlike the volume of papers of Professor 

 Tait, noticed above, this volume of the papers 

 of Professor Eeynolds has both a table of con- 

 tents and an index. 



Every one interested in the progress and in 

 the diffusion of science will hope that the 

 ' liberality of the Syndics of the University 

 Press,' under whose auspices these and similar 

 volumes have appeared, will continue to chal- 

 lenge admiration and commendation by the 

 republication of additional collections. 



E. S. W. 



Kleiner Leitfaden der praJctischen Physik. By F. 



KoHLEAUSCH. Leipzig, B. G. Teubuer. 



1900. 



Even the teachers of physics in America are 

 so familiar with the original ' Leitfaden ' that a 

 review of this abridgment may well be essen- 

 tially a comparison. The term Leitfaden (lead- 

 ing strings) expresses so well what is necesssary 

 in a laboratory that it is to be regretted that we 

 have no English equivalent. As the preface of 

 the smaller book indicates, the larger later edi- 

 tions of the original have become at once a 

 book of instructions and of reference, and has 

 suffered as do all books which grow in that 

 way. The new material is seldom well com- 

 bined and coordinated with the old. In the 

 new book the author has commenced all over 

 again and distributed the matter consist- 

 ently. 



It is called a smaller guide and yet it is neces- 

 sary to make a detailed comparison in order to 

 discover that some thirty-four paragraphs have 

 been either omitted or considerably condensed 

 and simplified. It is, however, still a very re- 

 spectable university course in physical labora- 

 tory work, and any student who thoroughly 

 masters it will be found well equipped for ad- 

 vanced work. It in no sense can be called an 

 elementary manual. It does not involve mathe- 

 matics higher than algebra and simple geometry 

 and trigonometry, logarithms and sines, cosines, 

 etc., are assumed. More diagrams and illus- 

 trations are used than heretofore and this seems 

 to be a real improvement. A picture book is 

 undesirable, but well chosen diagrams and dia- 

 grammatic sketches are a great help to the be- 



ginner. This has long been recognized in light 

 and electricity and should be judiciously ex- 

 tended. 



Condensation is too often opposed to simplifi- 

 cation, but in this case little or nothing of the 

 original clearness seems to be lost in the re- 

 arrangement. Nevertheless some good hard 

 thinking and strict attention will be required if 

 the student is to get full benefit. 



A chapter on the C. G. S. system of units is 

 placed at the very beginning, and is necessarily 

 very brief, and, although very important, may 

 well be used as matter for reference from time 

 to time as the units arise rather than to be 

 learned at the outset. 



Considered from the point of view of the 

 teacher in the general physical laboratory, this 

 book may well supplant the earlier treatise and 

 relegate it to the shelf with other books of ref 

 erence, and to the advanced special laborator- 

 ies. It is perhaps well to warn those less familiar 

 with the subject and with German idiom that 

 many words which are identical with the Eng- 

 lish are used in a different sense ; e. g., hydro- 

 meter, in English is equivalent of araeometer, 

 but Kohlrausch applies it to the communicating 

 tubes used for densities of liquids. In fact in 

 the chapter on the absolute units it would be 

 essential that a student have the technical Eng- 

 lish equivalents, and even then some of the 

 German units seem to be superfluous repeti- 

 tions, and it should be always left clearly im- 

 pressed upon the mind that 'work,' for ex- 

 ample, is always work and always measured 

 in the same unit no matter how the work may 

 be accomplished ; and similarly with other 

 units. 



The sections on light and especially on elec- 

 tricity and magnetism are very good and com- 

 plete. The diagrams in the electrical measure- 

 ments leave nothing to be desired and make 

 one regret that the author did not see fit to 

 illustrate the other subjects with the same 

 liberality and good judgment. 



A few useful tables and a good alphabetical 

 index contribute largely to the usefulness of 

 the book, which will be welcomed by every 

 laboratory instructor in physics in college or 

 university. 



W. Hallock. 



