130 Dr BREWSTER on a New Analysis of Solar Light. 



half of the whole spectrum. If we examine the blue and indigo 

 spaces through certain yellow fluids, such as oil of olives, &c. they 

 acquire a distinct violet tint, so that these fluids must have absorbed 

 some rays which had neutralized or masked the red. This violet 

 tint is still more distinct when the spectrum is examined through 

 a pale red glass, which exercises a powerful action upon the rays 

 between b and F in FRAUNHOFER'S diagram, combined with a 

 very pale yellow glass. In this case the violet extends to F nearly 

 at the limits of the blue space. The conversion of the whole of 

 the blue and violet space into violet, or what is the same thing, 

 the existence of red light in these spaces, may be exhibited in a 

 very palpable manner by the absorptive action of the yellow juice 

 of the Coreopsis tinctoria, when it has been rendered a bright 

 orange red by carbonate of soda, and is used in a state of consider- 

 able dilution. Red light therefore exists in the blue and indigo 

 spaces ; and, as I shall afterwards shew that white light, which 

 necessarily includes red, may be insulated both in the green and 

 yellow spaces, it follows that red light exists in all the seven 

 coloured spaces into which the spectrum is divided. 



Yellow light is distinctly recognised by the eye in the orange, 

 yellow, and green spaces which occupy 77 parts of the spectrum, 

 whose length is 360. When the spectrum is examined with a 

 deep blue glass, the green light is distinctly seen at F, one of 

 FRAUNHOFER'S lines ; and as a green transparent wafer of gela- 

 tine produces a whitish band beyond F, and in the blue space, it 

 is clear that a certain portion of yellow light must exist there. 

 We have already seen that the action of oil of olives on the blue 

 and indigo spaces absorbs certain rays and leaves a violet tinge. 

 These rays cannot be red, and they are not blue, because blue 

 taken from blue would not leave violet. They must, therefore, 

 be a small portion of yellow rays, which, forming white with the 

 red, and a portion of the blue, had the effect of diluting the pre- 

 dominant blue light. The existence of both yellow and red rays 



