268 



NA TURE 



[January 18, 1906 



There is no doubt that the kind of first course 

 laid out in this book is the right one from a psycho- 

 logical point of view. A quite young pupil, actually 

 carrying- out its directions with the help of a sympa- 

 thetic teacher, will obtain clear conceptions of 

 geometrical facts in a way that is really interesting 

 and fruitful. The apparatus required is of the 

 simplest possible kind — paper, pins, a pencil, and a 

 pair of scissors are all that are absolutely necessary, 

 though a compass and a scale might be provided 

 with advantage, except at the beginning of the 

 course. The attention given to solid figures is a 

 feature which deserves commendation; and above all 

 there does not seem to be anything said that is likely 

 to lead to misapprehensions, which have to be pain- 

 fully corrected afterwards. 



There are .1 few points of detail which might be 

 attended to in another edition. The letters in the 

 diagrams are too small; the figure on p. 151 does 

 not correspond to the text; on p. 35, "This gives us 

 another axiom" is quite illogical; and there are 

 some technical terms which might have been spared. 

 It must be remembered, too, that this is not a book 

 for a beginner to learn in the old-fashioned way; it 

 is intended to make him experiment and think, and 

 the guidance of the teacher is essential. Assuming 

 this, the book ought to be very useful, and lead to 

 good results, even in the case of pupils who have little 

 faculty for demonstrative geometry. 



G. B. M. 



LEGIBILITY AND VISUAL ACUITY. 

 Pliysiologie de la Lecture et de I'Ecriture. By Emile 



Javal. Pp. xv + 296. (Paris: Felix Alcan, 1905.) 



Price 6 francs. 

 ' I '"HE title of this book, which is written by a dis- 

 ■*- tinguished ophthalmologist, is somewhat mis- 

 leading. One would naturally expect such a work 

 to deal with the neuro-muscular mechanism, central 

 and peripheral, of reading and writing. In reality, it 

 treats almost exclusively of the legibility of printed 

 and written matter, and the physiological processes 

 are investigated only in so far as they throw light 

 upon this aspect of the subject, and give indications 

 for increased facility and rapidity in reading. 



In the first part of the book a brief historical account 

 of epigraphy, writing, typography, stenography, 

 musical notation, and writing in relief for the blind 

 is given. Typography is illustrated by examples from 

 Garamond (i$4o), adopted by Plantin, of Antwerp, 

 and the two Elzeviers, of Leyden and Amsterdam re- 

 spectively, from very elegant designs by Jaugeon 

 (171.4), and from the Imprimerie Imperiale (Didot, 

 1S11) and the Imprimerie Nationale (Marcellin 

 Legrand, 1847). Theoretical considerations of visual 

 acuity, treated in the second part, show that the 

 visibility of a letter increases indefinitely with the 

 illumination, whereas its legibility depends upon the 

 neuro-epithelial mosaic of the retina, and is therefore 

 independent of illumination above a certain minimum. 

 Investigation of the mechanism of reading a line of 

 print has shown that the eyes move in a series of 

 NO. 1890, VOL. J $] 



jerks, in each of which a group of about ten letters 

 is appreciated, the grouping being independent of the 

 distance of the book from the eyes so long as this 

 is consistent with legibility. Bar reading gives some 

 indication of the relative part played by the two eyes 

 when binocular vision is present. The difference of 

 accommodation in different parts of a line when the 

 book is held close to the eyes, as in myopia, is very 

 appreciable, and must be taken into account in treat- 

 ment; thus in a myope of 15 dioptres a line of 10 

 centimetres involves a difference of accommodation of 

 about 7 dioptres. The characteristic features of letters 

 are for the most part in the upper portion, so that 

 attention is specially directed here; consequently it is 

 easy to read with the lower halves of the letters 

 covered, whilst the reverse occasions considerable 

 difficulty. These considerations indicate some im- 

 provements in typography. They have been carried 

 out in some designs prepared for the author by M. Ch. 

 Drey fuss. It will be admitted that the result is 

 successful as regards legibility and rapidity of read- 

 ing, though at no small cost to the artistic sense. 

 M. Javal points out that nearly all the improvements 

 are to be seen in the well known enamelled-iron 

 advertisement of Willing; indeed, English printing as 

 a whole compares favourably in his estimation with 

 that of other countries. 



The terrible misfortune of blindness overtook the 

 author a few years ago, so that it is not surprising 

 that he has given much attention to Braille type. 

 Even those born blind rarely attain to a rate of 100 

 words a minute in reading, or 10 in writing. It is 

 surprising to find that the tactile acuity of the blind 

 is actually less than that of normal people ; the read- 

 ing finger tires rapidly, and though the acuity of 

 other fingers is greater, they are comparatively useless 

 for reading. The author gives valuable suggestions 

 for improving and simplifying Braille type, as well 

 as general instructions as to the hygiene of vision 

 and of writing. J. Herbert Parsons. 



OUR BOOK SHELF. 



Exercises in Quantitative Chemistry. By Harmon 

 Northrop Morse. Pp. xx + 356. (Boston and 

 London : Ginn and Co., 1905.) Price 8s. 6d. 

 The time when the sole desideratum in the training 

 of the chemical student was the acquirement of 

 greater or less proficiency in the processes of analytical 

 chemistry has, happily, gone by. Courses of experi- 

 mental work arranged with the view of familiarising 

 him with the most important general reactions, the 

 preparation of typical organic compounds, and the 

 methods peculiar to physical chemistry are now recog- 

 nised as the essentials of chemical training. The 

 work under review has been written from this stand- 

 point, and makes no attempt to present a course of 

 work for the training of expert analysts. 



Although much diversity of opinion must necessarily 

 attach to the problem of the choice of an ideal course 

 of exercises, the unbiased critic can have but little 

 fault to find with the author's selection. At first 

 sight the heterogeneous character of the sixty-four 

 1 :en 1 es creates an impression of a lack of systematic 

 arrangement, but this is more apparent than real. 

 The first eight chapters deal with the balance, the 



