57 



THE POPULAR SCIENCE MONTHLY. 



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 inter- 

 cepted by wicker traps or eel-sets placed 

 across the river, and in one of which 70,000 

 have been caught in one night. The mov- 

 ing of the fish is done in the night and al- 

 ways 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 col- 

 umns. They will surmount almost any ob- 

 stacle, creeping wherever there is any moist- 

 ure, through grass, and over stones and tim- 

 ber. These "eel-fairs" last through sev- 

 eral 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 riv- 

 ers 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 num- 

 bers remain. The migrations have been 

 generally supposed to be for breeding-pur- 

 poses ; 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 ovipa- 

 rous 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-set- 

 ters declare that it is viviparous ; " that 

 they have constantly opened eels in Febru- 

 ary 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 pa- 

 per 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 with- 

 out 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 char- 

 acter. 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 ori- 

 gin 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 af- 

 fections 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 abra- 

 sions 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 



