102 



LORD RAYLEIGH ON THE COLOURS OF THIN PLATES. 



The fact that the spectrum colours lie, roughly speaking, upon two sides of 

 the triangle (see Plate X.), indicates that all pure oranges and yellows can be 

 made up by a mixture of pure red and pure green, and in like manner that 

 all varieties of pure blue and blue-green can be compounded of pure violet and 

 pure green. If, as there is reason to believe, the curve representing the 

 spectrum is slightly rounded off at the green corner, this means that the 

 same spectrum green is not available for both pure yellows and pure blues. 

 The green lying most near the corner gives with red yellows, and with violet 

 blues, which are somewhat less saturated than the corresponding colours of the 

 spectrum. 



Table II. 





Sin*^ 









A 





- 



V = 1846 



V=3600 



V-6800 



16 



•607 



•896 



•828 



20 



•490 



•991 



•420 



24 



•367 



•980 



•060 



28 



•275 



•892 



•013 



32 



•188 



•737 



•225 



36 



•118 



•553 



•572 



40 



•066 



•379 



•863 



44 



•028 



•219 



1-000 



48 



•003 



•068 



•865 



52 



•000 



•024 



•702 



56 



•007 



•000 



•391 



60 



•026 



•026 



•148 



64 



•052 



•081 



•023 



68 



•084 



•164 



•008 



72 



•119 



•256 



•089 



76 



•164 



•373 



•264 



80 



•209 



•483 



•467 



84 



•255 



•589 



•667 



88 



•297 



•678 



•817 



92 



•342 



•762 



•932 



96 



•389 



•840 



•994 



100 



•440 



•904 



•989 



§ 4. The colours of thin plates are to be calculated in accordance with (2) 

 from Table I., as white was calculated, but with introduction throughout of the 

 factor sin 2 (7rV/X). For each thickness of plate V is constant, but an integration 

 over the spectrum is required. Table II, gives a specimen of the- values of the 

 factors, and may be considered to represent the brightness, at various points, 

 of thespectrum that would be formed by analysing the light reflected. The 

 three retardations given correspond to the reds of the first and second order, 



