Page:Popular Science Monthly Volume 16.djvu/600

 spears, or hook and line, serve the purpose; but, in order to supply the now enormously increased demand, drift-nets are used. These are three quarters of a mile in length, twenty feet in depth, and have a mesh sufficient to allow the head of a fish to enter as far as the gills. The fishing-season lasts from April to July, and during this time the work is prosecuted with vigor. Everything required in the business is manufactured on the premises. Foreigners are employed to do the work; Italians capture the fish and Chinamen prepare it for consumption. The fish, placed in racks in quantities, at the entrance of the cannery, are readily accessible. A flexible water-pipe directs its searching flow of water on to the salmon to cleanse them, after which they are sorted and placed within reach of the first operator. He takes off head, fins, and tail; making an incision into the back, the intestinal matter is removed, and the fish thrown into a tub half filled with water. The second operator scrapes and washes it, and passes it on to man number three for inspection. The fourth person ranges the bodies in a trough, where by means of blades driven by a crank they are cut to pieces. These are now neatly packed in cans, a spoonful of salt is put into each one, the lid is soldered down, and the cans are then ready for the cooking-house. Here immersed in a huge steamer they cook an hour. Removed from the steam-bath, they have each a small hole bored in them, to admit of their quickly cooling. The tins are next placed in boiling salt water, where they remain two hours. They are again examined, now to see that the ends have assumed a concave shape. Such tins as have not taken this shape are condemned, while all others are passed forward to be varnished and labeled. Before being sent to market they are again examined, and imperfect cans are rejected.

Voice in Fishes.—Sir. S. E. Pool, in a late number of "Nature," gives an account of an interesting observation of his own in support of the claim that fishes possess a faculty of voice. He states that, when engaged in a survey of the "Disang River in eastern Assam" some six years ago, he had occasion to sound the depth of a pool. When seated in a small canoe and slowly nearing it, he suddenly became aware of the presence of a number of fish called "mahsir." They were evidently attracted by the canoe, and Mr. Pool surmised that they might possibly think it a huge dead fish. While watching their movements, he became "aware of a peculiar 'cluck' or percussive sound—frequently repeated, on all sides, and coming from below," but near by. This was soon traced to the mahsir, and one of them made distinct sounds which were answered by others. He further states that in some parts of eastern Assam a large bivalve sings in concert with others.

Expansion of Bodies by Electrification.—In a communication to the Paris Academy of Sciences, E. Duter describes some experiments which have led him to the conclusion that bodies are increased in bulk by electrification. A large thermometer-tube is filled with water and coated externally with tin-foil, forming a Leyden-jar or condenser, with the water for the interior conductor, the foil for the exterior conductor, and the tube for the insulator—a platinum wire dipping into the water as a charging rod or electrode. As soon as the jar is electrified the water sinks to a lower level, and so remains till the jar is discharged. The inference is, that the glass is dilated by electrification, and this inference is strengthened by the fact that the same effects are produced whatever be the nature of the armatures, whether tin-foil, water, saline or mercury solutions. To remove all doubts, M. Duter modified the apparatus by placing the tube (or Leyden-jar) in a closed envelope of glass, terminated also by a thermometer-stem and filled equally with a liquid conductor. In this arrangement the liquid of the internal reservoir formed the interior armature of the condenser, and the liquid of the envelope formed the exterior armature, the glass tube being, as before, the insulator. On electrification, while the inner liquid sank, the outer liquid rose to an equal amount, thus proving the accuracy of the inference. On discharge of the electricity, the original levels were restored. The conclusion is, that the internal capacity of a Leyden-jar and its external volume are increased by charging it with static electricity. Temperature can not cause this