As an example of the method by which this admirable effect is produced, let us take a small portion of the wing of the Peacock, a very beautiful, though an abundant species, and one admirably adapted for microscopic examination, and to illustrate the subject, from the great variety of rich tints brought together in a small space, the part selected being the eye-like spot at the outer corner of each upper wing. Even to the naked eye this appears as a very splendidly coloured object, yet but little of its exquisite mechanism can be discovered by the unassisted organ. Something more is brought out by a moderately strong lens: we then see the colours disposed in rows, reminding us of the surface of Brussels carpet, or of certain kinds of tapestry work.
Now let us place the wing on the stage of a good microscope, with the root of the wing pointing towards the light (that is the best position for it); we shall then first perceive that the whole surface is covered, or, so to
speak, tiled over with distinct, sharply cut scales, arranged as in fig. 16, [Plate II]., with the outer or free edges of one row overlapping the roots of the next. These roots being all planted towards the base of the wing, if we place that end next the light (as above directed), the free edges of the scales throw a strong shadow on the next row, which brings out the imbricated effect most strikingly.
Beginning our observations at the outer edge of the wing, we first notice a delicate fringe of scales or plumes, more elongated and pointed than the surface scales, and of a quiet brown colour. This tint is continued inwards for a short space, gradually lightening, when (as we shift the field of view towards the centre of the wing) the colour of the scales suddenly changes to an intense black; then a little further, and the black ground is all spangled with glittering sapphires, then strewed deep with amethyst round a heap of whitest pearls. Golden topaz—(jewels only will furnish apt terms of comparison for these insect gems)—golden topaz ends the bright many-coloured crescent, and in the centre is enclosed a spot of profoundest black, gradating into a rich unnameable red, whose velvet depth and softness contrast deliciously with the adjacent flashing lustre; then comes another field of velvet black, then more gold, and so on till the gorgeous picture is complete.
Subject a piece of finest human painting to the scrutiny of a strong magnifying glass, and where is the beauty thereof? Far from being magnified, it will have wholly vanished: its cleverest touches turned to coarse, repulsive daubs and stains.
Now, bring the microscope's most searching powers to bear upon the painting of an insect's wing, and we find only pictures within pictures as the powers increase; the very pigments used turn out to be jewels, not rough uncut stones, but cut and graven gems, bedded in softest velvet.
If by gentle rubbing with the finger-tip the scales be removed from both sides of the wing (for each side is scale-covered, though generally with a very different pattern), there remains a transparent membrane like that of a bee's or fly's wing, tight stretched between stiff branching veins, but bearing no vestige of its late gay painting, thus showing that the whole of the colouring resides in the scales, the places occupied by the roots of the latter being marked by rows of dots.