Page:Popular Science Monthly Volume 33.djvu/735

Rh objects were formed by easting in molds. Hammering was but little practiced, excepting apparently in the formation of sheet gold, which was probably an indigenous product. Repoussé work is not found, save as represented in the crimping and indenting of gold-leaf. Engraving and carving were not practised. It may be deemed certain that gilding, or at least plating, was understood.

Fish-ponds.—The making and maintenance of fish-ponds is one of the arts in which man—at least until within a dozen years past—has not advanced. It was better and more extensively cultivated in antiquity and the middle ages than now. And there is still no better authority on the subject than Bishop Dubravius, of Olmutz, of the sixteenth century. He advised a regular draining of ponds, and cropping them with vegetables and grain in alternation with the fish. He would have three ponds, with a three years' rotation of vegetable crops, grown and breeding fish, and fry, so that the proprietor would always have a crop of vegetables growing in one pond, yearling fry in another pond, and breeders with the fish fattening for the market in the third. Captain Milton P. Pierce, of the American Carp Cultural Association, recommends draining the ponds every spring as early as the weather will permit, to promote the growth of aquatic vegetation, and another draining in October for the purpose of assorting the carp. He uses three ponds, all at the same time for fish, but does not advocate the rotation and planting system of Dubravius. Opinions differ as to the expediency of allowing trees to grow along the margins of fish-ponds. They harbor insects and so contribute to the supply of food, but their falling leaves are litter and make the water unpleasant. Frank Buckland recommended the hanging of a dead cat or rabbit over the pond, to be a nursery for "gentles"—plainly maggots—which would fall into the pond and afford excellent food for the fish. The presence of ducks is of great advantage, for they dig up the mud in the bottom, exposing the organic life it contains, and also increase the insect-breeding capacity of the mud—all helping to furnish the fishes' dinner-tables. A similar effect follows allowing cattle to come and stand in the ponds. The ponds should not be too deep, and large ponds have several drawbacks which are absent from small ones. There are advantages and disadvantages about having a stream run through the pond; hence it may be well to arrange so that the stream can be turned on or carried around at will. A "collector"—a wooden box, four feet deep by five square, sunk flush with the pond, with a perforated inner box that can be drawn up—is a convenient appendage. When the pond sluice is opened, the fish will go into the deepest water, which is in this collector, whence they can be drawn out and sorted. The collectors also may supply the place of the deep retiring holes which fish are fond of resorting to. Some breeders furnish a hedge in the pond as a shelter. A fattening tank affords a convenient means of securing a constant supply of fish ready for the table and easy to be caught. To supply food for the fish, Herr Fruwirth, of Austria, has pools and ditches with stagnant water and aquatic plants, wherein all kinds of insects etc., breed, which he turns into the ponds from time to time. Dr. Kelsen, of Oxford, has discovered that the animalculæ bred in water containing decayed vegetable matter are eagerly devoured by the young fry. Captain Milton Pierce says that nursery ponds in good condition and provision will support from one thousand to fifteen hundred yearling carp per acre area of water. Stock ponds, in like condition, will support five hundred two-year-old carp per acre. Larger stocks should not be permitted. Only one kind of fish should be allowed in the pond at a time. Where there are many varieties, they come to little good, and eat one another up.

Watering the Floors as a Preventive of Coal-Mine Explosions.—Mr. W. Galloway, believing that coal-dust is a very active cause of mine explosions, and usually even a more important factor than gas, recommends watering or simply dampening the floors of mines as an efficient preventive of them. In support of his theory he cites the case of the explosion of the Pochin colliery, in November, 1884, where the flame, which had been very powerful, was found to have been arrested by a slight dampness—such only as was caused by the casual leakage