January 28, 1916] 



SCIENCE 



125 



Beyond question, the greatest present 

 need of applied optics is cooperation. 

 Workers in one field are often lacking in 

 knowledge of the data, methods and princi- 

 ples developed by those in other fields. 

 For example, the illuminating engineer de- 

 sires more complete information relating to 

 photometry, radiation laws, scattered light, 

 and above all on the properties of the retina 

 upon which depend the conditions for best 

 illumination. Such information is difficult 

 to obtain in any case and much of it is not 

 available at all. Again, either the eye or a 

 photographic plate is an essential part of 

 every optical instrument, yet what designer 

 of optical instruments posesses a full 

 knowledge of the characteristic properties 

 of either ? The ophthalmologist desiring to 

 know more of the nature and properties of 

 light is confronted by a highly technical 

 mass of information, largely in mathemat- 

 ical language and almost useless to him. A 

 great many persons, vitally interested in 

 the color of materials, are almost entirely 

 without information as to the precise an- 

 alysis or synthesis of color. Nearly every 

 one could make good use of a knowledge of 

 the conditions of illumination conducive to 

 the best seeing, yet evidences of profound 

 ignorance of those conditions are on every 

 hand. Similar instances of lack of coor- 

 dination of interests in applied optics might 

 be multiplied indefinitely. 



We believe that such a condition of 

 affairs is best met by the formation of such 

 a society as this. It is our aim to provide 

 for the free interchange of ideas in the 

 meetings of this society. A clearing house 

 and a storehouse of data and information 

 will best be provided by the establishment 

 of a journal for the publication and dis- 

 semination of new and useful material in 

 the various fields of applied optics. As 

 soon as such material shall have reached a 

 permanent form, it should be crystallized 



in convenient books of reference. The need 

 for the organization, the journal, and for 

 reference texts will hardly be questioned 

 by any one. 



Aside from the need for cooperation and 

 the dissemination of the knowledge already 

 available in the various fields of applied 

 optics, the great need is for more informa- 

 tion along various lines. It is a fitting oc- 

 casion to briefiy review the several branches 

 of applied optics, calling attention to fields 

 of research in which investigation appears 

 to be most urgently needed. 



The very ground work of all applied op- 

 tics is of course pure optics. Little prog- 

 ress can be made without a thorough 

 knowledge of the laws of the refraction, re- 

 flection, absorption and emission of light, 

 nor of diffraction, interference, scatter or 

 polarization. Most of these laws are well 

 known and familiar but there are conspic- 

 uous exceptions of vital importance in ap- 

 plied optics. The laws of radiation appli- 

 cable to a perfect radiator are fairly com- 

 plete but very little is known of the cor- 

 responding laws applicable to the practical 

 case of heated bodies or to gases conducting 

 an electric current. While the laws of re- 

 flection and refraction are commonly con- 

 sidered well known, as a matter of fact we 

 know almost nothing of the laws applicable 

 to a layer whose thickness is comparable 

 with the length of a light wave. In this 

 case practise has not waited for theory, 

 for lens surfaces are said to have been pre- 

 pared giving greatly decreased loss of light 

 by reflection. Another and conspicuous 

 gap in our knowledge of pure optics relates 

 to heterogeneous media. Light is scattered 

 by small particles and absorbed by still 

 smaller ones but very little attention has 

 been given to the laws governing the scat- 

 ter and diffusion of light so important in 

 illuminating engineering. 



In the field of lens calculation, though 



