REVIEWS 153 



for their benefit a certain amount of dictation or blackboard writing is essential. 

 At Gresham's School all the notes were dictated until the author tried the plan of 

 distributing the printed notes on which this book is based. It is claimed that the 

 experiment has proved a success — " fifty per cent, more ground is covered, and the 

 boys understand the work just as well." Against it there is the objection that 

 the acquirement of the art of note-taking is a not unimportant part of an 

 elementary science course. Moreover, even if notes be distributed, each teacher's 

 course should have an individuality of its own which would lose much by being 

 tied down to a precise scheme drafted by another. 



In the cheaper edition of the book the left-hand pages are left blank so that 

 the students themselves may draw on them the diagrams which form so important 

 a part of an elementary light course. The complete edition, with diagrams, is 

 intended as a key for the master's use. This plan is novel so far as physics books 

 are concerned, and its advisability must depend on the capabilities of the class. 

 The notes themselves are clear and concise, covering the ground of a school 

 course in geometrical optics of perhaps a little more than matriculation standard. 

 A little adverse criticism is necessary. The fact chosen to disprove the corpuscu- 

 lar theory is unfortunate : "... if the corpuscles travelled with this enormous 

 velocity they would possess a considerable momentum, of which there is no 

 evidence." This is, of course, incorrect, even though that which exists is only a 

 second order quantity ; the true criterion might easily have been given. Four 

 of the diagrams showing the paths of light rays through telescopic systems 

 (pp. 184 and 186) are very misleading in that the rays leaving points on the 

 images are not the same as those arriving at them, so that, apparently the rays 

 are bent in passing through a focus. Experience in marking examination papers 

 shows how prevalent this error is. The descriptions throughout are written with 

 the personal pronoun "we did . . .," "we took . . .," "we drew . . .," etc. ; even 

 at school boys should be taught to write impersonally. A word of praise must be 

 given to the way in which the book has been produced ; the paper, printing, and 

 diagrams are altogether admirable. 



D. O. W. 



A Textbook of Physics. By J. Duncan, Wh.Ex., M.I.Mech.E., and S. G. 

 Starling, B.Sc, A.R.C.Sc. [Pp. xxiii + 1081, with 985 figures in the 

 text.] (London: Macmillan & Co., 1918. Price 15^. net. Also issued in 

 Parts : Dynamics, 5.?. ; Heat, Light, and Sound, 6s. ; Magnetism and 

 Electricity, 4s. ; Heat, 3.?. 6d. ; Light and Sound, 3^. 6d.) 



This textbook is intended primarily for the use of students of engineering, and 

 the subject-matter has been chosen consistently with that end in view. The first 

 300 pages form a complete treatise on elementary mechanics. Stress is laid on 

 graphical methods, and the examples are such as are of special interest in 

 engineering work. The section on heat includes an account of combustion and of 

 calorimeters designed to measure the thermal value of various fuels ; there is a 

 good description of oil and steam engines, boilers, indicators, turbines, and even of 

 the Gaede molecular air-pump. Viscosity has, however, been overlooked, and the 

 treatment of surface tension and osmotic pressure is very brief. In light special 

 attention is given to surveying instruments ; in electricity to dynamos, motors, and 

 alternators. Taking the book as a whole, the material has been selected with 

 excellent judgment, is up to date, and is such as is not to be found in any other 

 book of its kind. 



