[turnbull] a subjective PHENOMENON OF VISION 



21 



one candle power and, after reflection from the " black " object and 

 absorption in the glass plates, hardly any light could have reached the 

 Fovea; (2) represents the intensity of the light from an ordinary fish- 

 tail burner after reflection and absorption as before: 



Remarks. 



No. of 

 Readings 

 in each 



Set. 



Coloured 

 glasses used ; 

 short rest after 

 every 2 read- 

 ings. 



do. readings 

 taken at an- 

 other time. 



No. of 



Sets. 



Colour 



and 



Intensity 



Ri 



Ro 



Gi 



Go 



IBi 



IB, 



Ave. 

 Period- 

 icity. 



Further Remarks. 



.482 

 ..510 



.498 

 .528 



..502 

 ..528 



..520 



..548 



.508 

 532 

 7512' 

 .522 



The intensity (1) repre- 

 sents the periodicity 

 (almost) for the sensation of 

 black in the case of all of 

 the colours used (as ex- 

 plained in the text above) ; 

 and therefore no conclus- 

 ions regarding the change 

 in periodicity brought about 

 by change in intensity can 

 be drawn. 



Do. — More accurate re- 

 sults with 3 different inten- 

 sities follows in the latter 

 part of the experimental 

 work. 



do. 



do. 



do. 



do. 



