On this subject one of the latest observers of humming-birds, Mr. Everard im Thurn, in his work on British Guiana, has the following passage:--"Hardly more than one point of colour is in reality ever visible in any one humming-bird at one and the same time, for each point only shows its peculiar and glittering colour when the light falls upon it from a particular direction. A true representation of one of these birds would show it in somewhat sombre colours, except just at the one point which, when the bird is in the position chosen for representation, meets the light at the requisite angle, and that point alone should be shown in full brilliance of colour. A flowery shrub is sometimes seen surrounded by a cloud of humming-birds, all of one species, and each, of course, in a different position. If someone would draw such a scene as that, showing a different detail of colour in each bird, according to its position, then some idea of the actual appearance of the bird might be given to one who had never seen an example." It is hardly to be expected that anyone will carry out the above suggestion, and produce a monograph with pages ten or fifteen feet wide by eighteen feet long, each one showing a cloud of humming-birds of one species flitting about a flowery bush; but even in such a picture as that would be, the birds, suspended on unlovely angular projections instead of "hazy semicircles of indistinctness," and each with an immovable fleck of brightness on the otherwise sombre plumage, would be as unlike living humming-birds as anything in the older monographs.