282 THE POPULAR SCIENCE MONTHLY. 



fleeting part ; and the color of the reflected light depends upon the 

 angle of the incident ray to the surface, and varies as the angle varies. 

 In one direction of the incident ray, the light will be wholly absorbed, 

 and, none being reflected, the surface will appear intensely black. It 

 will readily be perceived that every movement of the bird produces 

 more or less a change of color. Even the heaving of the breast, in 

 breathing, sometimes produces jDerceptible changes. 



The nests of humming-birds are curiously, skillfully, and quickly 

 made. Most of them are formed of the down of the gigantic silk- 

 cotton tree, or other vegetable fibres, worked into a sort of wadding 

 or felt, and covered on the outside with particles of lichen, moss, webs 

 of spiders, etc., the saliva of the bird being used to assist in holding 

 the parts together. They are generally cup-shaped, or conical. Mar- 

 tin says : " In position, these nests are as different as imagination can 

 conceive. Some are attached to the fork of a branch ; others are bound 

 to a waving twig enshrouded by foliage ; others are pendent, attached 

 to the extremity of the leaves of palms, flags, and other plants, over- 

 hanging water; others, again, build on rocks, hanging their nests by 

 filaments to the sides of bold precipices; others hang their nests to 

 the extremity of slender, pendent tendrils. Their eggs are two in 

 number, white, but often, from their transparency, they display the 

 color of the yolk, the shell appearing as if tinged with a blush of 

 orange-red or pink. The eggs are a long oval, measuring, on the aver- 

 age, from three-eighths to one-half of an inch in length." Captain 

 Lyon, writing from Gongo Soco, Brazil, says : " It may interest you to 

 have an account of some young humming-birds, whose hatching and 

 education I studiously attended, as the nest was made in a little orange- 

 bush, by the side of a frequented walk, in my garden. It was composed 

 of the silky down of a plant, and covered with small, flat jjieces of 

 yellow lichen. The first Qgg was laid January 26th, the second on the 

 28th, and two little creatures, like bees, made their appearance on the 

 morning of February 14th. The old bird sat very close during the 

 continuance of the heavy rain for several days and nights. The young 

 remained blind until February 2Sth, and flew on the morning of March 

 7th, without previous practice, as strong. and swiftly as the mother, 

 taking their first start from the nest to a tree about twenty yards dis- 

 tant." The intense activity of humming-birds makes it necessary for 

 them to have food containing nitrogen, which they get by feeding on 

 insects. Honey furnishes proper food, or fuel, for the lungs, but it 

 alone cannot form muscle, or give strength. They resemble the swifts 

 in their powers of flight ; the woodpeckers, in their means for dart- 

 ing out the tongue ; and the sunbirds, in the metallic lustre of their 

 plumage. 



The ruby and topaz, or ruby-crested, humming-bird [Chrysolam- 

 pis moschitus, Boie) derives its common name " from the color of its 

 head and throat, the former being of a deep ruby tint, and the latter 



