IN ITS RELATION TO THE EYE. 465 



while in case of the opaque reflectors the significant variations in the 

 Hghting effects were produced by changing the size (more especially 

 the depth) of the reflector, the lining and the design. Of these Re- 

 flector IV. was of blown silvered glass with a system of spiral 

 corrugations on its reflecting surface for the diffusion of light. This 

 reflector was of the deep bowl type, lo^/^ in. in diameter and ii^ 

 in. deep. Reflector V. was also of blown silvered glass and had a 

 vertical system of finer corrugations than had Reflector IV. This 

 reflector was 9% in. in diameter and 8 in. deep and was more dis- 

 tributing in type than was Reflector IV. Both of these reflectors 

 were used with 3J4 hi. form "A" holders. Reflector VI. was a 

 steel, aluminum-finished reflector of the intensive type, 8>4 in. in 

 diameter and yYz in. deep. This reflector was provided with a clip 

 ring which was attached directly to the socket. Reflector VII. was 

 a porcelain-enameled steel reflector of the shallow dome or dis- 

 tributing type, 15 in. in diameter and 6^ in. deep. This reflector 

 was used with a 2^ in. form " O " holder. 



Early in the work with these reflectors it was found that if 

 good results for the eye were to be obtained with dense or com- 

 pletely opaque reflectors, some way must be gotten either of shield- 

 ing the eye from the opening of the reflector or of reducing its bril- 

 liancy which increases as the density of the reflector is increased. 

 Obviously something can be accomplished in this direction by using 

 reflectors of the deep bowl type, giving specular rather than diffuse 

 reflection, if the angle of presentation to the eye is not too great. 

 Reflector IV., for example, is of this type. The opening of this 

 reflector was of low brilhancy when viewed at an angle of 13° 19', 

 the angle of presentation to the eye for the two reflectors farthest 

 from the observer in the present series of experiments. High up in 

 the reflector, however, was a small but brilliant image of the lamp, 

 a part of which was visible at an angle with the eye of 20° 17', the 

 angle made by the two reflectors at Outlet B ( Fig. i ) , and still more 

 at an angle of 40°, the angle made by the two reflectors nearest the 

 observer. It was thought advisable to find out how much this re- 

 flector could be improved in its effect on the eye by reducing the 

 amount of reflection for a certain distance above the lower edge of 

 the reflector. This was accomplished for the purpose of these ex- 



