Page:Popular Science Monthly Volume 36.djvu/146

136 of water, no longer retarded by the atmosphere and descending as rain would be unable to obtain food, from inability to move themselves by any ordinary method of locomotion, or, what would be equally serious, having once started into motion, from being unable to stop except when they came into collision with other unhappy beings or moving bodies. Before long they, with all heavier substances, would disappear forever beneath the waters which would now cover the face of a lifeless world."

British Whales.—The whales of the British Islands are more abundant and more varied in species than has generally been supposed. The most important of the species that have occurred in Great Britain is the Greenland right whale, which has now been driven into the far north. The Atlantic right whale was once hunted with considerable vigor in the English Channel; and those who hunted it there are said to have invented the harpoon, and taught the Dutch whalers how to use it. The hump-backed or Bermuda whale has been cast ashore on the islands, and is therefore entitled to be called a British species. A fourth species is the caaing or bottle-nose whale, a large school of which was seen in the summer of 1888 disporting in the Bay of Firth. The whale—an air-breathing mammal living in the water—is admirably adapted to its environment. The blow-holes are placed on the top of the head, and the animal can respire only when they are above the water. The animal heat is preserved and the specific gravity reduced by the thick coating of blubber that lies just under the skin. An interesting trait in the economy of the whale is the manner in which it suckles its young. It partly turns on its side, and the teats being protruded, sucking and breathing go on simultaneously. The "baleen" or whalebone of the "whalebone whales" consists of about five hundred laminæ—taking the place of teeth—ranged about two thirds of an inch apart, and having their interior edges covered with fringes of hair. Some of them are fifteen feet long. The cavity of a whale's mouth has been compared with that of an ordinary ship's cabin, the inside of which is covered with a thick fur. The soft, spongy tongue is often a monstrous mass ten feet broad and eighteen feet long. The whale feeds upon minute mollusks—Medusæ and Entomostraceæ—with which the northern seas abound. "Opening its huge mouth," says Prof. Huxley, "and allowing the sea-water, with its multitudinous tenants, to fill the oral cavity, the whale shuts the lower jaw upon the baleen plates, and, straining out the water through them, swallows the prey stranded upon its vast tongue."

Standards of Light.—It is a delicate matter to obtain an accurate standard of light. Candles are still most relied upon for the tests of comparison, but it is obvious that they are susceptible of great variations in the intensity of the light they afford. Still, if made according to fixed rules, and their burning similarly regulated, they will give a fair approach to accuracy. Various English acts prescribe a sperm candle of six to the pound, and burning at the rate of one hundred and twenty grains per hour; also that the tip of the wick shall be glowing and slightly bent. Gas examiners are not always as particular in the matter as they ought to be, and, by allowing the wick to remain upright, may obtain a result indicating a gas of slightly more value than it really has. The German Gas and Water Society recommend an amyl acetate lamp, which is not quite as intense as a candle, and is objected to by Mr. W. J. Dibdin as being unsuitable in the color of its light. Dr. Werner Siemens has devised a selenium photometer, the electric resistance of which is exactly dependent on the light falling upon it. The pentane lamp, and the Methven screen, in which a coal-gas light is admitted through an aperture of fixed dimensions, are favored by many persons; and a standard afforded by a melting or a solidifying platinum wire is well spoken of.

John Mercer, F. R. S.—John Mercer has been called by Mr. T. E. Thorpe, in "Nature," the "Palissy of calico-printing." He achieved a great success in the arts without any other helps than those which he made for or attracted to himself. He was born, according to Mr. E. A. Parnell's "Life," in 1791, the son of a hand-loom weaver, who had turned to agriculture. When nine years old, he was set to work, on the death of his