Page:Popular Science Monthly Volume 23.djvu/587

Rh Musical Fishes.—Cases of peculiar sounds being heard at sea and ascribed to fishes are not rare. Lieutenant White, of our navy, relates that, when at the mouth of a river in Cambodia in 1824, he and the crew of his vessel were struck by hearing extraordinary sounds, like a mixture of the bass of an organ, the ringing of bells, the guttural cries of a large frog, and the tones of an enormous harp, which they heard around the bottom of their vessel. The interpreter said they were produced by a troop of a kind of fish. Dr. Buist, in 1847, told of a party in a boat near Bombay, who heard sounds not unlike the others, which the boatmen said were produced by fish. Similar sounds were reported two years afterward as having been heard from beneath the water at Vizagapatam. Sir J. Emerson Tennent heard like sounds from the Lake of Batticaloa, in Ceylon, and the natives said that a shell made them. A correspondent of the "Field," in 1867, alleged that the vessel in which he was at Greytown, Nicaragua, was haunted at night by these sounds. A similar account, probably of the same occurrence, is given by Mr. Dennely, in "Nature" of May 12, 1870. Another correspondent of the "Field" told of sounds "produced by fishes" which he heard in the Tavoy River. A review of all the accounts shows that the sounds were nearly always heard in ships at sea, though Canon Kingsley once heard them at Trinidad from the shore; that they are most commonly heard in tropical regions, but sometimes in the temperate zone; that they have been noticed along an extensive line of coasts, American, European, and Asiatic, northern and southern; that they are invariably heard at night; and that they are most generally heard near the mouths of rivers. Dr. Dufossé, who has made the production of sound by fishes a special study, says that, while many fishes can make themselves heard, there is a great variety in the manner in which the noises are evolved. Sometimes they proceed from the movements or friction of the pharyngeal bones, or the vibration of the muscles of the swimming bladder. In the latter way a gurnard produces nearly an octave of notes. The males of the genus Ophidium are provided with a drumming apparatus, consisting of bones and muscles developed in relation to the swimming-bladder. The sounds made by the Umbrinas of the Mediterranean have been heard from a depth of twenty fathoms.

Action of Acids on Tin-Ware.—Mr. Francis P. Hall reports the results of experiments on the action of vegetable acids—acetic, tartaric, and citric acids—on lead and tin. The results were rather negative in their tendency, and seem hardly to bear out the assertions that are made respecting the danger of lead-poisoning from tinned goods. The most danger is from the solder, and from the action of the acids on the tin itself. The corrosion does not appear to increase as regularly as is supposed with the strength of these acids; but it was found that corrosion, in the case of canned fruits, takes place very rapidly after the can is opened, so that a can when opened should be emptied at once. Mr. Hall's analyses of bright tin-plate failed in every case to show enough lead impurity to justify the charge of intended adulteration, even in the worst looking ware from the five-cent stores. Terne plate, used for roofing, is known to contain large quantities of lead, but no one with his eyes open is ever likely to buy it for genuine tin. Tin-foil, which is used for enveloping various kinds of food, is in some cases pure tin, in other cases heavily adulterated. Specimens used for wrapping different kinds of compressed yeast were pure. The worst specimen (89·87 per cent lead) was embossed, and on a very fashionable cake of chocolate.

German Explorations in Africa.—The Germans claim the honor of having done the most after the English for the exploration of the interior of Africa. The trading posts of the Hamburg merchants on the east coast have long exercised a civilizing influence there. To German missionaries are due the first important discoveries that were made in that region, viz., the discovery of Mount Kilimanjaro by the missionary Rebmann, in 1848; that of Mount Kenia by the missionary Krapf, in 1849; and the execution of a map of the country, showing the Ukerewe Lake, by Rebmann and Erhardt, a work which provoked the English expeditions of Burton, and of Grant and Speke. Dr. Albert Roscher planned the ascent of