Page:Popular Science Monthly Volume 47.djvu/588

574 it were perpetrated in the name of public utility. Even the French for once agreed with the English about what should be done in Egypt. The plan was changed. The majestic structure of the dam will be cut down thirty-seven feet, so as to be only eighty-eight feet high, and Philæ will stand in a lake, but will not be drowned.

Patinas of Japanese Bronzes.—Describing the patinas of Japanese bronzes, Mr. W. Gowland, late of the Imperial Mint, says that in many bronzes the beautiful color is due to a "stain" or colored film of infinitesimal thinness. In others, the surface of the metal is altered to a considerable depth, and in these only we have true patinas. Frequently both a stain and a patina are produced by similar treatment, but the operations required for the latter are of a more prolonged character than for the former, and are accompanied by special manipulations in addition to the application of what are called pickling solutions. For the production of patinas of the richest and darkest shades of brown by Japanese methods, it is essential that lead should form one of the constituents of the bronze, and that zinc should either be absent altogether or be present only in small proportions. On the other hand, stains of any color can be given to metal of any composition, and even to unalloyed copper. The substances used in the operations are copper sulphate, basic acetates of copper (verdi-gris), iron sulphate, sulphur in fine powder, alum, vinegar prepared from unripe plums, and a decoction of the roots or entire plant of Calamagrestis Hakenensis (natural order Gramineæ), potassium nitrate, and sodium chloride. The most important of these reagents are the first five. The processes for producing a patina by the use of the various solutions of these substances are somewhat complicated and difficult, and the intermediate operations, on which its production depends more than on the exact composition of the solution, are variously modified in different foundries.

The Peril of Color-Blindness.—Renewed attention has been called by Surgeon W. M. Beaumont, of the Bath (England) Eye Infirmary, to the importance of perfect color vision for railway servants, which is unquestioned in the minds of ophthalmic surgeons, however other doctors and railway directors may be disposed to ignore it. Some questions asked by one of the doubting doctors, whether, since attention has been turned to the subject, any accident has been brought home to defect in color vision, or other facts demonstrating the theory have been brought out in usual practical sailing and railway life, are answered by reference to several illustrative incidents that have been gathered. Of these are the wreck of the steamer City of Austin, on the Florida coast, with a color-blind pilot; the collision of the Corbet Castle and the T. H. Ramieu, due to the color-blindness or short-sightedness of the chief officer; the collision of the Lumberman and the Isaac Bell, near Norfolk, Va., the Lumberman's master being color-blind, and consequently taking the wrong course with his vessel; and the narrow escape of the steamer Neera from a collision through the color-blindness of its officer. In another instance the color-blindness of a railway fireman and the imminent danger of collision thereby were experimentally determined in the ordinary working of the train. Even where the color-blind engineer believes he can distinguish between the signals, and appears to do so, he does it, not by the color, but by the difference in intensity. This is a very uncertain and indefinite factor, and is liable to variations according to the weather, the condition of the engineer, and other causes not so well known, and can not be safely depended upon.

Farming on the Yang-tse Kiang.—The country in China along the Yang-tse River from Shanghai to Hankow, and for a hundred miles on either side of the river, is, in general, a rich alluvial plain, traversed by ranges of hills having an east and west trend. The tops of the hills give the best tea, and where the ground is stony fir and oil trees are planted, for oil, resin, timber, and firewood. On lands of intermediate height—or where the land is not suitable for rice—cotton, wheat, corn, buckwheat, sweet potatoes, and kitchen vegetables are grown in great profusion. Dairy farming is unknown, and milk is looked upon with disgust. The native buffalo is the domestic animal employed in cultivating rice. Three crops can