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on an average, of one soldier in every fifty-five unable to distinguish 

 a scarlet coat from green grass would not issue in grave inconve- 

 nience, and ere this have forced itself into prominence by pro- 

 ducing mischief. Among the circle of my own personal acquaint- 

 ance I have only known two (though, of course, I have heard of 

 and been placed in correspondence with several) ; and a neighbour 

 of mine, who takes great delight in horticulture, and has a superb 

 collection of exotic flowers, informs me that among the multitude of 

 persons who have seen and admired it, he does not recollect having 

 ever met with one who appeared incapable of appretiating the variety 

 and richness of the tints, or insensible to the brilliancy of the nume- 

 rous shades of red and scarlet. It may be, however, that the per- 

 centage is on the increase certainly we hear of more cases than 

 formerly ; but this probably arises from the fact of this, like many 

 other subjects, being made more generally matter of conversation. 



In further reference to the question of the superposition of colours 

 in the spectrum, or of the intrinsic compositeness of rays of definite 

 refrangibilities, I may mention a phenomenon which I have been 

 led to notice in the prosecution of some experiments on the photo- 

 graphic impressions of the spectrum on papers variously prepared, 

 which appeared to me, when first noticed, quite incompatible with 

 the simplicity of those rays at least which occupy the more luminous 

 portion of the spectrum, extending between the lines marked D and E 

 by Fraunhofer, and clearly to demonstrate the presence of green 

 light over nearly the whole of that interval. In these experiments 

 the spectrum formed by two Fraunhofer flint prisms, arranged so as 

 to increase the dispersion, and adjusted to the position of least de- 

 viation for the yellow rays, was concentrated by an achromatic lens, 

 and received on the paper placed in its focus, which could be viewed 

 from behind. A series of white papers impregnated with washes of 

 various colourless or very slightly coloured chemical preparations, 

 and dried, were exposed ; and the spectrum being received on them, 

 and the centre of the extreme red image as viewed through a stand- 

 ard glass, adjusted to a fiducial pinhole ; a sensitizing wash of nitrate 

 of silver, or any other fitting preparation, was copiously applied to 

 the exposed surface while under the action of the light. Now, under 

 these circumstances, I uniformly found that whereas the spectrum 

 viewed from behind through the paper exhibited all over the space 



