Page:Popular Science Monthly Volume 45.djvu/300

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THE POPULAR SCIENCE MONTHLY.

increased worrying of horses by flies before rain, and the rise of the gossamer before fine weather, are abundantly confirmed by observation.

 

Habits of Birds.—Many interesting notices, local and general, respecting birds are to be found in the Abstract of the Proceedings of the Linnæan Society of New York for the year ending March 1, 1893. Frank M. Chapman, reporting at one of the meetings on the summer bird life of New York and vicinity, said that 127 species might be classed as summer residents, of which 108 were land birds and 19 water birds; 22 species might be considered abundant, 47 common, 31 tolerably common, and 27 rare. Dr. C. S. Allen contributed at another meeting an account of a breeding-place of pelicans on an island of Florida, a hundred and fifty feet long by fifty feet broad, and covered with a dense growth of mangroves. The nests were in bushes, ten or fifteen feet from the ground, were made of sticks, straw, dry weeds, etc., and held from one to four eggs. The young, on emerging from the shell, are of a size corresponding with that of the egg, and slate-colored, from tint of skin, with apparently scattering hairs (casings) protecting white down; but in a few hours they appear to have increased to several times the bulk of the egg, and become white as soon as the down is freed from the protective covering; in a few days they are as large proportionately as birds usually are when a week or two old. The increase in size is due, in part, to the power the birds have of taking air into the spaces beneath the skin which is very loose and capable of being immensely inflated. They remained in the nest only a few days, and thereafter rested on the surrounding bushes. Mr. Chapman instanced a number of cases of protective coloration, notably that of a flock of parrots flying into a palm tree, whereupon they became almost indistinguishable from their surroundings, although not hidden to any extent by the foliage. He described, as illustrating the fact of the bird's consciousness of its protective coloration, the habit the Cuban meadow lark has of turning its back to the observer, and also the instance related by Mr. W. H. Hudson, in his Argentine Ornithology, of a wounded bittern which persisted in turning its breast toward its captor, although he endeavored to pass around behind it. The bird, with its slender neck pointing straight upward, could not be distinguished from a seed stalk, except on close scrutiny. Mr. Chapman said that Dr. John A. Wells, of Englewood, N. J., had recently watched a woodcock on her nest, and was fully convinced that she was aware of her resemblance to the surroundings, for she remained perfectly quiet and allowed of a very near approach; but when a fall of snow came, and Dr. Wells again visited the sitting bird—now a very conspicuous object—she flew before he had approached within gunshot. The most notable example of protective mimicry is the European cuckoo, which, by reason of its striking resemblance to a hawk, is able to deposit its eggs in the nests of other birds, while they chatter and scold at a respectful distance. Together with many other notices of this kind, the Abstract of Proceedings contains a paper by Tappan Adney giving a list of bird names, etc., of the Milicete Indians of the St. John Valley, New Brunswick.

 

Measuring the Heights of Clouds.—Four methods of measuring cloud heights have been used at Blue Hill Observatory, Massachusetts: 1. The bases of the lowest clouds frequently float below the summit of the hill (one hundred and twenty-six metres above the general surface of the surrounding land), and the altitude of the base can be ascertained by walking down the side of the hill. 2. Measurements of the angular altitude of the light reflected from clouds floating over adjacent cities can be used for determining the height of the clouds. 3. The shadows of detached clouds can be seen from Blue Hill for many miles moving across the surface of the country, and, by timing the movements of the shadows between points whose distance apart is known, the velocity of the cloud can be ascertained. From the actual velocity and the angular velocity of the cloud its height can be determined. 4. Simultaneous angular measurements of the altitude and direction of the same cloud-point have been made at two stations eleven hundred and seventy-eight metres apart. An attempt has also been made to determine the height