504 Capt. W. de W. Abney. Examination for [May 14, 



This name must evidently have been a mental distinction, as si 

 described the red end and the white as grey only, and not brown- 

 grey ; and, indeed, she was tried again over that part of the spectrum, 

 and adhered to the previous naming. It would appear to be due to 

 the low luminosity which made the grey appear brownish to her, and 

 not to any actual difference in hue. 



Her curve of luminosity in the spectrum was next taken, and her 

 readings are given in the table. The curve is shown in fig. 5. The 

 shaded band beneath it applies to her curve. My own readings were 

 1/1 '375 of the normal curve as shown in the diagram. The extinction 

 of a gas-light, in my own case and that of Mr. Nettleship, was 13'5. 

 That of N. W. was 16, showing that her final perception of light was 

 13'5/16 of what we may call the normal. 



An endeavour was made to form a series of colour equations with her 

 eyesight by placing three slits in different parts of the spectrum, but 

 without success, although a match with white was made in two posi- 

 tions. One slit was placed in the orange-red at about 52 of the scale, 

 another at E, and the third at Gr, and white light was formed, though 

 her match was so erratic that it was useless to measure the apertures. 

 When the slit in the violet was covered up, a white patch being along- 

 side as a comparison, she called the mixture of red and green 

 u brownish-green ; " when the slit in the red was covered she called 

 the mixed light of green and violet "green;" and when the green 

 Blit was covered up she called the purple colour a " different kind of 

 brown." 



When the first slit was moved into the red near the lithium line she 

 called the colours "green," whenever the green slot was uncovered. 

 A piece of signal-red glass (London, Brighton, and South Coast 

 Railway) was placed in the white reflected beam, forming a red patch, 

 and a patch of the blue scale at No. 30*5 (X 4862) was placed 

 alongside, and she matched them in luminosity and in colour. (The 

 dominant colour of the signal glass in question was X 6220.) She 

 finally was tested with colour discs : 



One being in red with dominant wave-length . . X 6150 

 Another, emerald-green . . X 5373 



And the third, French ultramarine . . X 4700. 



To make white she required 



130 G + 113 R+117 U = 72 W + 288 B (corrected). 



She was then tried with the blue and green discs alone and made a 

 match 



258 U + 102 G = 65 W + 295 B (corrected). 



An attempt was made to match with the green and red discs alone, 

 but this failed. 



