Apbix 8, 1910] 



SCIENCE 



541 



is no matlieinatics, and throughout there is 

 evidence of a desire to make the book attract- 

 ive to the non-technical reader. It is some- 

 v^hat doubtful, however, vehether the book will 

 appeal to many except students or technical 

 men who desire a brief but comprehensive 

 survey of certain phases of illuminating 

 engineering. As a whole the book is suggest- 

 ive, and should be of distinct value in help- 

 ing to correlate the various phenomena of 

 physics and physiology on which the scien- 

 tific side of illuminating engineering rests. 



It would scarcely seem, however, that a 

 text-book for students, or an exposition for 

 the general educated public, should be the 

 proper place to introduce new ideas and terms 

 which have not yet been accorded general ac- 

 ceptance by scientific writers, and yet the 

 present book contains many such innovations. 

 Wave-lengths are expressed in micro-centi- 

 meters (cm. X 10"°) on the ground that there 

 are several other systems in use, none of 

 which is scientifically accurate (p. 7) accord- 

 ing to the C.G.S. system; and yet several 

 pages further on (p. 16) a sudden jump is 

 made from centimeters to feet. The classifica- 

 tion (p. 20) of " the total range of known 

 radiations " into " the electric waves and the 

 light waves " would scarcely seem orthodox or 

 clarifying, particularly as the " light " waves 

 are made to include even X-rays. 



In Lecture IX. a number of types of pho- 

 tometers, some of them quite primitive, are de- 

 scribed, and several pages are given to a de- 

 scription of a so-called " luminometer " which 

 employs the old but sometimes very useful 

 method of " reading distances," whereas no 

 mention has been found of one of the most 

 common, and perhaps the most accurate pho- 

 tometer in use at the present day for comparing 

 lights of approximately the same color — the 

 Lummer-Brodhun photometer in its two 

 forms. Even the very familiar Bunsen 

 photometer, though mentioned by name, is 

 nowhere described. The photometer shown in 

 the diagrammatic sketch and described under 

 the name " Bunsen " on page 170 is in reality 

 a simple Ritchie wedge, distinctly different 

 from the " grease spot " photometer invented 



by Bunsen, or even the more recently im- 

 proved Leeson disk which is sometimes substi- 

 tuted for it. Again (p. 260) it would seem 

 that too little weight is given to the accepted 

 definition of " illumination " compared with 

 the author's idea of what this term should in- 

 dicate. 



Lecture III., Physiological Effects of Eadi- 

 ation, would seem to the reviewer to be very 

 unfortunate in its manner of presentation. As^ 

 the present knowledge in this field, particu- 

 larly in regard to the " pathological and other 

 effects on the eye," is quite restricted, and 

 only to a very limited extent satisfactorily es- 

 tablished, one is likely to wonder whether the- 

 many positive statements are correct expres- 

 sions of accepted facts or merely speculation- 

 Here, particularly, a few references to author- 

 itative sources of information would be ap- 

 preciated. It is perhaps questionable whether- 

 the various harmful effects of light on the eye- 

 can be so readily classified into the two dis- 

 tinct groups, " power effects " and " specific- 

 effects of the shorter waves." It is quite prob- 

 able that a definite large amount of radiant 

 energy incident on the eye would be capable 

 of producing entirely different results if all' 

 of the energy were in the infra-red, or if all 

 were concentrated in the most luminous por- 

 tion of the visible spectrum. We can look at 

 an incandescent mantle or an incandescent 

 filament for a brief period without any pro- 

 nounced feeling of pain, but what would the- 

 result be if all of the radiant energy from 

 these sources could be transformed into light,, 

 even of the longer wave-lengths where the so- 

 called " specific effects " presumably do not 

 enter? The dazzling glare in such an experi- 

 ment, were it practicable, would very prob- 

 ably be distinctly painful. In general it i-s 

 necessary to consider the quality in conjunc- 

 tion with the quantity, so that the classifica- 

 tion suggested would scarcely seem justified.. 

 Moreover, it would seem wise to discriminate 

 between those effects which pertain to the- 

 anterior portions of the eye as in the absorp- 

 tion of large quantities of ultra-violet radia- 

 tion, and those harmful effects which are- 

 retinal. 



