>90 



NA TURE 



[July 30, 1908 



The metallurgy of iron and steel is well described, 

 but the discussions of the constitution of steel and 

 of the rusting of iron leave much to be desired. 



With all its imperfections, the " Treatise " is of 

 great interest and value. As has been said, its 

 strength lies in its descriptions of facts, which are 

 usually accurate and clear. Criticism and generalisa- 

 tion are both weak points in the work. The chemist 

 will, however, be thankful for a generally readable 

 account of the subject, and ev'en grateful to the author, 

 who has not been deterred from his task by the appal- 

 ling number and complexity of the facts of chemistry, 

 a circumstance which is chiefly responsible for the 

 calamity that the most notable treatise on chemistry 

 written in English in recent times, notable alike for its 

 grasp of detail, its power of generalisation, and not 

 least for its extraordinary clearness in brief descrip- 

 tion, never got beyond that first volume, which 

 astonished the chemical world nearly half a century 

 ago. 



TRACT ICAL PHYSICS. 

 Practical Pliysics : a Laboratory Manual for Colleges 

 and Technical Schools. By W. S. Franklin, 

 C. M. Crawford, and Barry MacNutt. Vol. i., Pre- 

 cise Measurements. Measurements in Mechanics 

 and Heat. Pp. vii+173. Price 55. net. Vol. ii.. 

 Elementary and Advanced Measurements i . l^iec- 

 tricity and Magnetism. Pp. vii-l-i6o. Price :.?. net. 

 Vol. iii., Photometry. Experiments in Light and 

 Sound. Pp. vii + 80. Price 45. net. (New York : 

 The Macmillan Co.; London: jNIacmillan and Co., 

 Ltd., 1908.) 



nPHIRTY years ago Prof. E. C./ Pickering: pub- 

 ■*- lished his " Physical Manipulation." .The whole 

 aim of the book, he told his readers, iwas to show 

 how work in the physical laboratory might be made 

 to teach a student to think for himself and to in- 

 vestigate; and in order to aid the instructor in the 

 cultivation of originality he added to the 200 experi- 

 ments described a hundred experimental problems as 

 suggestions of what the student might with advantage 

 be set to do. 



In the book before us Pickering's aim . has been 

 comoletely lost sight of. The authors reg'ard a 

 laboratory course for undergraduates as 

 " having a two-fold purpose. On the one hand it 

 serves to illustrate the principles of physics and their 

 application to actual problems. . . . On the other 

 hand it is intended to cultivate the power of accurate 

 observation, to familiarise the student with methods 

 of measurement, to give him skill and facilitv in the 

 use of measuring instruments, and to develop in him 

 the judgment necessary for the making of measure- 

 ments in a manner adeauate to the requirements of 

 science, engineering and commercial work." 



The character of the book is in close accord with 

 the authors' conception of the educational utility of 

 a laboratory course. 



(i) The discussions by which most of the ex- 

 perimental exercises are introduced, while suffi- 

 cient possibly for the objects in view, are in 

 general quite insufficient to give the student an 

 intelligent command of the methods involved. He is 



NO. 2022, VOL. ;?*• 



accordingly assumed not to have acquired it. There 

 is some discussion, e.g., of the balance and the baro- 

 meter, and of the corrections which observations 

 made with them may require, but the student is not 

 trusted, in exercises in which these instruments are 

 used, to settle the question of corrections for himself. 

 He is told whether or not he is to apply any, and if 

 any, which. 



(2) The student is encouraged to make unintelli- 

 gent use of formulae. For example, he is given the 

 expressions for the probable errors of an average and 

 of a single observation, with a statement of their 

 significance so short as to have a probable error of 

 its own, and he is then directed in exercise after 

 exercise to compute their values. He is not expected, 

 apparently, to make any use of the results of his 

 computations. 



(3) Correct procedure being essential to the acquisi- 

 tion of skill in measuring, the student gets full direc- 

 tions as to what he is to do. Thus in the case of the 

 Kelvin double bridge there is no general discussion 

 of the arrangement, but a cut of a particular form 

 of the bridge is given, and the student is even told 

 to which binding-posts he must connect the terminals 

 of his resistances and his galvanometer. The direc- 

 tions are not so detailed as this in all cases ; but the 

 course to be taken is in general fully pointed out. 



(4) The student is in no case set to the serious 

 investigation, or even testing, of physical laws. Per- 

 haps the nearest approach to work of this kind is the 

 study of the compressibility of air, and the following 

 is a slightly condensed extract from the directions to 

 the student : — 



"Tabulate the values of v(b±h) along with the values 

 of '' and (b±li), — the positive or. negative sign to be 

 used according as the pressure of the entrapped air 

 is greater or less than the pressure of the outside air. 

 Determine the mean of the tabulated values of 

 v{b±h), and tabulate the differences between this 

 mean and each of the tabulated values of -'(6 + /!). 

 These differences represent errors of observations. 

 Plot the pairs oi values of z< and b + h, usincr values of 

 V as abscissas and values of b + h as ordinates, and 

 draw a smooth curve among the points so plotted." 



There is little scope for the student's initiative here. 



As to extent, the book contains 132 selected experi- 

 ments. It does not claixn to be exhaustive. In the 

 selection the needs of the technical student have been 

 kept in view, and the advanced electricity and the 

 photometry are especially technical in their character. 

 Among somewhat unusual things which' are included 

 are the ^"enturi water-meter, flash-point determin- 

 ations, decomposition voltages, . mean horizontal 

 candle-power, and integrating photometry. .Among 

 important things omitted are thermoelectric and re- 

 sistance thermometry, ice and steam calorimelry, 

 quadrant electrometers, differential galvanometers, 

 Newton's rings, and cardinal points of lens systems. 



The book has minor defects due to insufficient edit- 

 ing of the laboratory direction papers on which it 

 appears to have been based. There are dreary repeti- 

 tions of similar, sometimes identical, directions. Un- 

 usual terms such as abampere are employed without 

 definition. There arc references to " the instructor " 

 which sliould have been replaced bv references to 



J 



