Page:Popular Science Monthly Volume 49.djvu/593

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clouds is shown when they sink rapidly; the dust is then seen at their edges and gives the iridescent or nacreous appearance frequently observed.


Horticulture an Object Lesson in Evolution.—The study of horticulture and agriculture is held up in Garden and Forest as having a distinct value as a factor in furnishing exercise for certain powers of the mind, and as providing in the systematic examination of the principles of those branches training than which no science affords better. Prof. Bailey, in Science, mentions some of the uses and applications of horticulture in discussing the theory of evolution. It shows the development of life in actual operation. More than six thousand species of plants are cultivated, and most of these have been broken up into varied forms by the hand of man. Some species have produced thousands of distinct forms, and the methods of production of many of them are on record. In place of arguments as to the probable influence of climate upon plants, the horticulturist cites definite cases, so that there is no conjecture about the matter. Instead of speculating upon the transmission of acquired characters, the horticulturist furnishes proof of such transmission. Paleontology brings disjointed evidence in regard to the influence of selection and probable changes from environment, while the horticulturist brings examples before our eyes to prove that he can modify and mold vegetation at his will. The horticulturist creates new species, and shows you numbers of cultivated plants of which no one knows the original form, because the ones with which we are acquainted are so unlike the type that the two can never be connected. This is only a single line of inquiry, and other illustrations quite as striking can be given to show that there is an abundant field for scientific research and profound thought in horticultural science as such.


Physical Characteristics of Cuba.—"In Cuba," says Mr. J. W. Spencer, in his paper on the Geographical Evolution of Cuba, "are mountains higher than any on the eastern side of North America; extensive plains as level as those of the Atlantic coast; valleys formed at the base-level of erosion, and deep cañons carved out by the youngest streams; the remains of enormous beds of limestones mostly swept off the country, and coral reefs and mangrove islands extending the coastal plains into the sea; sea cliffs, caves, and terraces of great and little elevation; drowned valleys deeper than the fiords of Norway indenting the margin of the insular mass; caverns innumerable and rivers flowing underground; rifts through mountain ridges and rock basins; tilted, bent, and overturned strata, dislocated and faulted in modern times, so as to make youthful mountain ranges; metamorphic rocks and rocks igneous, and these again altered to secondary products; old base-level plains or those modified and reaching across the island, having insular ridges of older formations rising out of them, and with the surfaces scarcely incised by the streams; residual soils from the decomposition of the rocks and sea-made loams and gravels; in short, so rapidly are the geologic forces working that one can see a greater variety of structure and learn more of dynamic geology in Cuba than on more than half of the temperate continent." The island is seven hundred and fifty miles long and from twenty-five to one hundred and twenty miles wide. In the western part the ridges of mountains culminate in a point with an altitude of twenty-five hundred feet, but the principal topographic relief is along the southern coast of the eastern extension of the island where Pico Tarquino rises from the Sierra Maestra to an elevation of eighty-four hundred feet. The central portion of the island is generally a plain of from two hundred to four hundred feet above tide, which bears many scattered and interrupted ridges like islands in a sea. Mr. Spencer's study is chiefly confined to this part of the island.


A Word in Favor of Woodpeckers.—The food of woodpeckers has been studied, with a view to determining whether they are injurious or beneficial in the economy of apiculture and forestry, by F. E. L. Beal, who concludes that they do far more good in the destruction of insects than harm with the little fruit and grain they eat and the sap they suck. Of seven species considered, the author regards the downy woodpecker as the most beneficial, it being a great eater of in-