_On the Juxtaposition of Coloured Bodies with Grey._ (See Plate 10, Page 58.) 63. As the brilliancy of the light reflected by white bodies is one of the principal causes which render the sight insensible to the modifications produced in white by the juxtaposition of coloured bodies; and, on the other hand, as the feeble light reflected from black bodies is unfavourable to our perception of the modifications which they sustain from the proximity of coloured bodies, especially when the complementary of the colour of these bodies is but slightly luminous, it may be conceived that grey bodies, judiciously selected with regard to their depth of tone, would, by contiguity to coloured bodies, exhibit the phenomena of contrast of colour in a more striking manner than either black or white bodies would. _Red and Grey._ 64. Grey appears Greenish by receiving the influence of its complementary Red. The Red appears purer, less Orange perhaps. _Orange and Grey._ 65. Grey appears Bluer by receiving the influence of its complementary Orange. The Orange appears purer, more brilliant, Yellower perhaps. _Yellow and Grey._ 66. Grey appears to incline to Violet by receiving the influence of its complementary Yellow. The Yellow appears more brilliant, and yet less Green. _Green and Grey._ 67. Grey appears to incline to Red by receiving the influence of its complementary Green. The Green appears more brilliant, Yellower perhaps. _Blue and Grey._ 68. Grey appears to incline to Orange by receiving the influence of its complementary Blue. The Blue appears more brilliant, Greener perhaps. _Indigo and Grey._ 69. Grey appears to incline to Orange by receiving the influence of its complementary Blue. The Blue appears more brilliant, Greener perhaps. _Violet and Grey._ 70. Grey appears Yellowish by receiving the influence of its complementary Violet. Violet appears fresher, less dull. 70_a_. The grey, which was the subject of the above experiments, was as free as possible from every colouring matter foreign to black; it belonged to the scale of normal black (see Part II., 164)—that is to say, it resulted from a mixture of the purest possible black and white materials. By juxtaposition with white, it appeared deeper, and the white appeared more pure; while by juxtaposition with black, it appeared lighter and more rusty, and the black appeared deeper. 70_b_. One result of the complementaries of colours in juxtaposition with grey being more perceptible than when these colours are juxtaposed with white or black, is, that if instead of a _normal grey_, we juxtapose a _grey, tinted_ either with _red, orange, yellow_, &c., these tints will be greatly heightened by the complementaries added to them. For example, a bluish grey will receive a very perceptible increase of blue from its proximity to orange, and a yellowish-grey will take a perceptible green tint from the same proximity.