Nov, 8, 1888] 



NATURE 



29 



vertical indices" receives special attention, and a sec- 

 ^tion on defilade— a subject not much studied in this 

 ^country — cannot fail to be of use and interest to those 

 who study the science of war. E. D. A. 



OUR BOOK SHELF. 



Examples in Physics. By D. E. Jones, B.Sc, Lecturer 

 in Physics at the University College of Wales, Aberyst- 

 wyth. (London and New York: Macmillan and Co., 

 1888.) 



5o many books have been written having titles similar to 

 ' not identical with that quoted above, the only object of 

 I'hich seems to have been to enable students to pass 

 certain examinations with theminimumof knowledge, that 

 it is a comfort to turn to one against which no such 

 charge can be made. Mr. Jones's " Examples in Physics" 

 has not been written " up to " any Syllabus, but the author 

 has made use of portions of the manuscript in teaching 

 classes of students taking the intermediate science and pre- 

 liminary scientific courses of the London University, and 

 he believes it will be found useful for students who are 

 preparing for these examinations. There can be no 

 doubt that the book will be of great assistance in this way, 

 owing to the large number of examples and the excellent 

 way in which they have been graduated. In addition to 

 the examples, of which there are more than a thousand, 

 with occasional hints for their solution, there are short 

 explanatory chapters and paragraphs where experience 

 has shown that they are needed. Thus, at the beginning, 

 the C.G.S. units are thoroughly explained, as is the 

 method of passing from one system of units to another by 

 means of dimensional equations. Those approximate re- 

 lations which are most often made use of are shown to be 

 true, and examples illustrating the advantage of employing 

 them are worked out. The method of using logarithms is 

 explained, and both on pp. 19 and 21 the reader is told 

 that there is a table of four-place logarithms at the end of 

 the book. There is a page on which natural sines and 

 tangents are given to three places, but not a vestige of a 

 logarithm is to be found. 



In the chapters on dynamics, hydro-statics, heat, light, 

 sound, electricity, and magnetism, chapters which consist 

 essentially of examples, there are clearly-written para- 

 graphs explaining those points that do not generally seem 

 to be grasped by students. The answers to the questions 

 are given at the end. 



The general arrangement of the book is particularly 

 happy ; it is clearly the work of a teacher whose object is 

 to increase the real knowledge of his students, and not 

 merely to drive them through the ordeal of an examination. 



The Constants of Nature. By Frank W. Clarke. Part 

 I. New Edition. (Washington : Published by the 

 Smithsonian Institution, 1888.) 



This volume consists of a series of tables of specific 

 gravities of solids and liquids, and differs from the older 

 edition in two respects. In the first place, the tables have 

 been revised and greatly enlarged ; and, secondly, melting 

 and boiling points have been omitted, on the ground that 

 they are already supplied by the two volumes by Prof. \ 

 Carnelley, which are specially devoted to those data. ; 

 How much the tables have been enlarged may be 1 

 gathered from the fact that the older edition, with a later | 

 supplement, only gave 2963 substances, whereas there are : 

 now no less than 5227 distinct substances mentioned, and j 

 14,465 separate determinations. As the author remarks, j 

 this increase is a noteworthy indication of chemical j 

 activity. 



The tables are only intended to be complete as far as , 

 artificial substances of definite constitution are concerned, | 



but, in addition to these, many minerals find places. For 

 each substance, the formula, specific gravities, and 

 authorities are stated. The elements take the first place, 

 and these are arranged in order of densities. Then follow 

 inorganic fluorides, chlorides, bromides, iodides, oxides, 

 sulphides, &c., the various groups of organic bodies 

 coming last. There is a very complete index to the names 

 of substances, without which, of course, the book would 

 be far from complete. 



The author is to be congratulated on the successful 

 completion of an undertaking entailing such a vast amount 

 of patient labour. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he under- 

 take to return, or to correspond with the writers of, 

 rejected manuscripts intended for this or any other part 

 of Nature. No notice is taken of anonymous communi- 

 cations.^ 



Gresham College. 



I TRUST you will allow me space for a short note upon Prof. 

 Lankester's article in last week's issue of Nature (p. i), under 

 the above heading. I have no intention of entering into a con- 

 troversy with Prof. Lankester upon matters of opinion, but I 

 am desirous of correcting statements, made by him in that article, 

 which are inaccurate. In point of fact, the article is based 

 entirely upon a misapprehension as to the purpose and function 

 of the London Society for the Extension of University Teaching, 

 and its position with regard to Gresham College. Prof. Lan- 

 kester speaks of it as a Lecture Society, and refers to the "in- 

 numerable short courses " of lectures given in different hails, 

 Vestry Halls, and others in London. He is evidently here con- 

 fusing two distinct things. The short courses in large halls are 

 given under the People's Lectures Scheme, which is an entirely 

 different matter, and in connection with which we never use the 

 word " University." The courses of lectures and classes carried 

 on by the London Society and the Universities Joint Board 

 involve a systematic course of work extending over a full term 

 of ten or twelve weeks. It is a part of the same great move- 

 ment which is carried on by the University of Cambridge (not 

 by a Lecture Society), and more recently also by the University 

 of Oxford, in different parts of the country. 



Those who have had an insight into the methods and the 

 result of the working of the University Extension movement have 

 been struck with the excellence and thoroughness of the work 

 done. Sir James Paget, in his annual address to students at the 

 Mansion House, last February, spoke as follows with regard to 

 some of the syllabuses : — 



"As I looked through the syllabuses of such subjects as I can 

 estimate, I could see that the amount of teaching in each of them 

 is enough for a good beginning for some who may intend to 

 make that subject a chief study for their lives, and enough to 

 form an important part in the teaching of anyone who wishes to 

 be in the fairest sense generally well educated." 



In fact, the principles which underlie the University Extension 

 movement cannot but meet with the approval of all interested in 

 higher education. These principles are, " first, that the amplest 

 facilities for the best kind of higher teaching, such as the Univer- 

 sities provide, should be brought within the reach of the great 

 mass of the people by means of courses of instruction, given 

 locally at convenient times and places ; and, secondly, that a 

 teaching system, as opposed to a mere examination system, is 

 required to meet the educational needs of the time." 



In his speech at Gresham College, Mr. Goschen made no 

 claim that " Gresham's money should be assigned to the support 

 of the lecturers of the Society." What he did point out was 

 that the design of Sir Thomas Gresham was to establish, in the 

 heart of London, University teaching for busy people engaged 

 in the City, and that the aim of the University Extension move- 

 ment, whether in London or the country, was in spirit the same. 

 Prof. Lankester charges this Society w ith making an obje'ction- 

 able use of the word " University " in order to gain financial 

 support. He says, " the implication is that the teaching is such 

 as is given at the Universities, and it is an entirely false implica- 



