ILLUMINATING ENGINEERING— A NEW PROFESSION. 



BY ARTHUR H, FORD. 



Since the time of the cave dwellers men have found artificial illu- 

 mination a convenience if not a necessity; but only within the present 

 century has the design of illumination system been considered for such im- 

 portance as to become a special branch of engineering. In fact the first 

 American college course bearing the name illumination was planned 

 and taught by the writer in 1901. This was given at the University 

 of Colorado and occupied two periods a week for a semester. The 

 profession is so new that it is not mentioned in even the most recent 

 dictionaries; so it is thought that it will be of interest to the members 

 of the Iowa Academy of Science to learn of the problems of the illu- 

 minating engineer and the materials with which he works. 



Roughly the problems may be divided into those of interior and ex- 

 terior illumination; the variety and number of the former being far 

 greater than the latter. It would seem to be a simple thing to light 

 a lecture hall, for example, so that it would be satisfactory for the 

 purpose desired ; but such is not the case, as the illumination of audi- 

 ence rooms is among the most difficult problems presented for solu- 

 tion. The requirements of such a place are that the speaker's face 

 shall be so illuminated that the persons in the audience can see his 

 expressions distinctly; next the audience shall be so illuminated that 

 the speaker can see the effect of his words and so get the proper reac- 

 tion; and finally the intensity and color of the illumination shall be 

 such the the audience is in the proper frame of mind. It is thus seen 

 that before the problem can be stated physically, in terms of illu- 

 mination, it must be solved as a problem of psycho-physiology, from the 

 primary data of the effect of light on speaker and audience. As an 

 illustration of the above statement the writer would call your atten- 

 tion to the instances where you have attended church in the evening 

 and been made drowsy ; supposedly by the dull sermon when as a matter 

 of fact it was by the bright choir lights which were within the range 

 of your vision. 



