Page:Popular Science Monthly Volume 27.djvu/588

570 base tastes. To these a Norfolk fisherman adds a fourth, the "hooking" eel or "gloat," of blackish color and medium size, which is taken by anglers and habbers and on night-lines, and does not migrate. The annual migration seaward of the sharp-nosed eels gives rise to the valuable eel-fisheries of the English rivers, in which the fish are intercepted by wicker traps or eel-sets placed across the river, and in one of which 70,000 have been caught in one night. The moving of the fish is done in the night and always in a dark night; and it is liable to be interrupted by a change of wind, a clap of thunder, or a clearing away of the clouds. What becomes of the immense numbers of eels that descend to the sea every season has never been found out. They are hardly missed from the haunts they have left; yet no one has ever seen any of them returning. In the spring, however, the young eels come up the rivers by millions, keeping close to the banks and swimming in almost solid columns. They will surmount almost any obstacle, creeping wherever there is any moisture, through grass, and over stones and timber. These "eel-fairs" last through several days; and the tiny elvers, about as large as darning-needle?, used to be scooped out by the bucketful and applied to the land for manure, baked into cakes for men, or used as food for pigs, until an act was passed prohibiting their destruction. The fact that eels that have once gone down the rivers never return is asserted positively by all who have observed them. The question is then in order, How is the supply in the rivers kept up; and how is it that the eels found in the rivers are of a large size? The answer is, that young eels are produced in the rivers, and that eels are so numerous that, although immense numbers leave the rivers every year, yet equally immense numbers remain. The migrations have been generally supposed to be for breeding-purposes; but there are reasons for believing that breeding takes place in the rivers as well as in the sea, so that this alone can not explain them; and it has been suggested that they are a kind of swarming, like that of bees, impelled by excess of numbers. Naturalists affirm that the eel is an oviparous animal, and that it deposits its spawn as other fish do, and point to the presence of spawn and milt in it as revealed by the microscope; but the eel-fishers and eel-setters declare that it is viviparous; "that they have constantly opened eels in February which have been full of minute living eels (not parasites), and that in a tub of eels young ones have been found in the morning that were not there overnight. . . . To use their own words, there are thousands and thousands of eel-fry all alive in the bodies of eels cut open in February."

Dangers from Industrial Dusts.—A paper was read by Dr. Henri Napias before the Congress of Industrial Hygiene, held at Rouen in July, 1884, on the dusts developed in industries and the methods of guarding against injury from them. Dusts in the air call for especial consideration, from the fact that, besides vitiating the atmosphere in the way that gaseous impurities also do, they exert a mechanical action when brought in contact with the respiratory and digestive system. Even when they are wholly without toxic or essentially irritant effects, they are foreign bodies and obstructive, and are always in danger of exerting a traumatic action or causing abrasions. They are, therefore, all dangerous, while the dangers arising from them may be various in character. Mineral dusts, whether of stones or of metals, are the most dangerous, because, besides being hard and sharp and liable to cut the tissues, very many of them are also poisonous or caustic. Dusts of organic origin are less dangerous, but they vitiate the air, communicate unpleasant qualities to it if they are of an animal nature, and are frequently vehicles for the conveyance of infectious germs. Various inconvenient affections of the lungs are caused by breathing these dusts, among which may be counted phthisis, not as produced directly by them, but as often ultimately induced by the abrasions or deterioration of the tissues which they immediately occasion. The readiest and most available means of removing dusts is by ventilation, and, when this can be so directed as to take them away as soon as they are formed, it is almost sovereign. It will not do, however, to rely upon general ventilation, for that will at most remove the dusts but imperfectly, while its usual operation will be more likely to distribute