NEW BOOKS

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NEW BOOKS Color a n d I t s Applications. B y JI, L i i r k i e s h -71 X 17 c.m; p p . vii T 357, SP.;~’ I h r k : D . T-ciiz Sostrcind ConipcLiiy, 191.i. Price: $3 .oo.-The aim of this book is t o present a condensed treatment of the science of color. T h e chapters are entitled: light: t h e production of color; color mixture; color terminology: t h e analysis ol color; color and vision: the effect of environment on pigments; theories of color vision : color photometry: color photograph?-; color in lighting; color effects for the stage and displal-s; color phenomena in painting; color matching; the a r t of mobile color; colored media. The following extracts, pp. 7 0 , 7 8 , 118,148, i 6 0 , 169, 2 , j z , 2 7 6 , xi11 give some idea of t h e contents of this very interesting book. “ T h e quality of any color can be accurately described by determining its hue, saturation or purity, and its brightness. ( T h e latter term is analogous t o the term ‘value’ as used by the artist.) In the broadest sense, white, gray, and black are here considered as colors, and a mere change in brightness alone is considered as a change in color. It appears necessary t o assume this broad definition of color, inasmuch as brightness is distinctly one of t h e products of color analysis. H u e is suggested in the name applied t o the color. T h e domin a n t hues of most colors are accurately represented by the spectral colors; however, there are composite colors-the purples, which consist of red and violet, for which no spectral colors are found t o represent their hues. In these cases i t is satisfactory to determine t h e dominant hue of the complementary colors. T h e saturation or purity- is a measure of the relative amount of white light in t h e color. In other words, all colors excepting purples can be matched by diluting spectral light of a definite wave-length with white light. The greater the percentage of white light required in the mixtures, the less saturated t h e colors are said t o be. T h e brightness of a color can be found by comparing i t by means of a photometer with a surface of known brightness. It is well t o note t h a t in t h e analysis of a color its absolute brightness is measured by comparing i t with a brightness of known value. Inasmuch as its brightness depends upon t h e intensity of illumination of a given spectral character, its reflection coefficient for a standard white light should be determined in order t o compare i t with other colors in this respect. ” Other sciences have exact a n d practically universally accepted terminology. Music has its well-developed notation, which is definite and descriptive [not when one considers tone] a n d quite universal in adoption; b u t there is no universal scheme of color notation. Colors are named in very inesact, unwieldy, a n d often totally non-descriptive terms. \Ye ha\-e rose, Indian red, Xlice blue, pea green, olive green, cerise, taupe, baby blue. Copenhagen blue, king’s blue, royal purple, invisible green, etc. T h u s flowers, vegetables, cities, the savage and t h e rol-a1 family, are used t o describe colors. I s there a more ridiculous instance of neglect? Those who work in color find themselves helpless in describing colors t o others. Surely a color notation based upon color science should be acceptable, even though somewhat empirical. l l u s i c a l notation is somewhat arbitrary, yet i t has met with almost univerqal adoption. -in ac‘ I

ceptable color notation must involve the factors n.hich influence t h e quality of a color, namely hue, saturation, and brightness.” ’‘-1 very striking experiment is found in focusing a line spectrum-that of mercury will suffice-upon a ground glass. On viewing it at normal distance ( 1 4 inches), t h e yellow and green lines will appear sharply focused, b u t t h e blue a n d violet lines will appear hazy and quite out of focus. On bringing the eye closer t h e latter lines will begin t o appear clearer, and finally. when the rye is within about six inches of them, they will still appear clear-cut. yhile it will be quite impossible t o accommodate the eye sufficiently to focus the yellow and green lines. In other words the eye is near-sighted (myopic! for blue rays and far-sighted (hyperopic) for red rays. On viewing a narrow continuous spectrum a t 5ome distance the blue appears t o flare o u t . . h o t h e r simple demonstration is found i n viewing a n illuminated slit through a d e i i ~ ecolialt glass which transmits estrcnie red and violet rays. On accommodating the eye for a point behind the slit a red imagc with a violet halo is seen. On accommodating for a point in front of the slit a violet image with a retl halo is seen. Thi? defect plays a prominent, though usually unnoticed, I1ai-t i n vision. =\ lens can be made practically achromatic by combining a convergent lens of c r o m i glass with a di\-crgent lens of flint glass. The formrr is more strongly convergent for blue than for retl rays, while t h e latter is more strongly divergent for blue t h a n for red lights. I? i i thus possible t o Ixing the rcd and blue rays in coincidence a t a focus. Inasmuch as i t is only possihle to bring two rays exactly into coincidence by a tn-o-piece lcns, such a lens is not truly achromatic, though practically so for most purposes.” “ I t is interesting t o note t h a t on a certain modern battleship a iighting system of blue lamps has lieen instaIleti for usc a t night when in a c t i o n The reason given for installing blue lights is t h a t they are invisible t o the enemy. KO inlormation was ol,tainalile a5 to whether the short range is due t o t h e faintness of the blue lights or to a supposed lowcr range for hlue t h a n for yellow light of equal intensity.” “In usiiig field glasses, distant \-ision can l)e i m p r o w d sometimes by t h e use of a light yeIlon. screen which climiiiatcs the blue haze from the visual image. In connection i t is ~ ~ t o1 note 1 also t h a t blue rays are normally o u t of focus a t the retina. The author ha.: experimented with colored screens for use with field glasses for detecting colored objects a t a distance by altering their contrast with their surroundings by the use of colored screens. For instance a khaki uniform (yellon-orange in color; can be made to appear either lighter or darker t h a n t h e green foliage surrounding i t bl- respectively using a yellow-orange screen or one of a complementary hue. For instance if the ratio of the brightness of a piece of khaki cloth to t h a t of a certain green leaf be taken as unity under daylight illumination, through a n ordinary orange filter this ratio became I j and through a blue-green filter, 0 . 7 . IVith care t h e contrast can be made practically a maximum. I n t h e case of objects more striking in color t h e problem is not as difficult. Tt’hetlier or not the reduction of brightness more t h a n offsets t h e advantage of increased contrast in distinguishing distant objects can be solved b y actual trial. T h e point is mentioned here t o illustrate t h e possibilities in t h e use of colored glasses as a n aid t o vision.” “Owing t o the surface character of colored media t h e distribution of light ,

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is of some importance in the consideration of the appearance of colors. Few pigments are applied in such a manner a s t o be perfectly diffusing, therefore some light is specularly reflected without having penetrated the pigment. This light is unchanged b y selective absorption a n d dilutes the light t h a t is colored b y penetrating the pigment and being selectively reflected. T h a t is, when the light is distributed in such a manner t h a t a n appreciable amount is specularlj- reflected into the eye of the observer the color appears less saturated. I n the extreme case of high specular reflection the pigment appears t h e same as a gray. -4 striking illustration of the effect of ciistriliution of light i i found in thc case of the so-called changeable silks. Such fabrics have a n a p , ant1 when t h e fibers end in the direction toward the light the latter penetrates the faliric and is deeply colored liy multiple -of colloidal solutions has to do particularly with its interest t o the student of physics. Both hy aim and necessity the writer has kept in mind the relation of colloids t o the development of phi-sics. For this reason rather extended treatment is given t o the del-elopment of the ultramicrowope and the confirmation of the kinetic theory of matter afforded b y t h e theoretical and experimental study of the Brownian movement. IVhen we come t o deal with the phenomena of the charge possessed h y the colloidal particle and the surrounding medium, a n d the mechanism of coagulation, we approach the most important prohlem of physics and chemistry, namely. the unfolding of the interaction of the ultimate particles of matter on one another." In the introduction, p. 1,the author s a y s : " T h e theoretical importance ol colloidal solutions is wide-spread; t o the physicist, probably their chief interest may be summed u p under three heads. I n the first place, the work of Einstein, Smoluchom-ski, and Langevin, in offering exact mathematical formulae whereby the Brownian mo\-ement may he quantitatively tested, and the investigations of Perrin o n the distrihution of the particles throughout the volume of a liquid, afford most striking evidence of the t r u t h of the fundamental hypotheses of t h e kinetic theory of liquids and gases, and of the existence of the molecule. Secondly, Faraday's work on the optical effects of such solutions has been recently supplemented by many researches which have been attempted to solve t h e riddle of the form and structure of the particles. Thirdly, the perennial question as t o the reason for the stability of these solutions remains. The various attractions or repulsions, physical forces which may be involved-electrical surface tension, molecular shocks-suggest a puzzle, the solution of which will undoubtedly give us most valuable information regarding t h e forms of energy involved in t h e liquid and solid states." The subject is treated under the general headings: preparation and classification of colloidal solutions ; t h e ultramicroscope t h e Brownian movement; t h e optical properties of colloidal solutions; measurement of t h e sizes of ultramicroscopic particles; motion of colloidal particles in a n electric field; the coagulation of colloids; theory of the stability of colloids: practical application of the study of colloidal solutions. ~

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Though the book is published in 1916, the manuscript was apparently finished before the middle of 1914. Consequently there is no general theory, and t h e author states explicitly t h a t a t t e m p t s t o account for the stability of suspensoids and emulsoids hy the same theory have been so unsuccessful t h a t we are forced t o treat these as two distinct classes. The chief value of t h e book thcrefore is in showing what parts of colloid cheiniqtry interest the phy-sicist.

Ti'ilder

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Rubber Machinery. R j 8Ii'rnrj C'. Pcciusoii. 23. X 17 C I H : p p . I-ork: Thc. l i i d i c i Rubhcr TT.or/ii. ~ y ~ Prirc: j . $6.00. In the preface the

author says: " F o r more than fiftl- year5 mechanical and iti\-enti\-e ingenuity has heen producing machinery for use in rulilier manufacture. In crude rubber washing. mixing antl calendering thc prolileni~were once thought t o lie comparati1;cIy simple and their iolu.tioii iiliout the same the world over. Today, howel-er, scores of uen- anti more efficient mnchines handle new gums and intricate compoundh, antl the 4rnplicity tlis:+pl)ears Even i n the preparation of the crude material for market. machiiiery i y t o a marked degree supplanting hand labor." The headings of the chaptvrs are : the v-a.;liing of crude ruhlicr ; crude rubher drying dr>---;extraction of rubber anti gutta percha from shrubs, vines, roots anti le:i\-es ; extraction ol' rvsin from rubber m t l gutta percha: reclaiming ; temperature recording and controlling clevices: rubber laboratory equipment. The book is illustrated profusely, averaging slightly over one c u t t o a page. The reviewer cannot speak for the rubber manufacturer b u t the book is certainly helpful t o the student. I t s value would I x increased hy- a more complete index, a n d i t is not quite clear why the chapters on ~-ulcanizingshould come before it7iiideu 11. R u i t i r i f t thoqc on spreaders, etc. ~

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Sec-oiid Editioii. 19 X 12 in?;p p . i t i TI^. In the statistical science5 we make great use of t h e theory of probability. \Ye cannot predict with any accuracy how long a n y particular man will live: h u t we know the average length of life of a m a n and the insurance companies work o u t tables which are sufficiently accurate when applied t o a large number of men. \Ye cannot predict whether a n y given child is t o be a boy or :L girl b u t we know t h a t o u t of a thousand children the probability is very strong of there being j r o boys. Throughout the liological sciences the theory of probabilities is of great w l u e . The author points o u t t h a t the kinetic theory of gases is chiefly a theory of probabilities and t h a t its q u a n t i t a t i w dewlopment really dates from the explicit recognition of this fact by LIaxwell. T h e book is distinctly an interesting one, though its value lies more in the possible broadening of the point of view t h a n in any conTli'lder D . Bancroft crete results t h a t may be obtained from it. Le Hasard.

B y l?niilc Borel.

P u r i s t FClis A / r a u , 1914. Prirr: 3 jofrcitics.