. The depths of the sea; an account of the general results of the dredging cruises of SS. 'Porcupine' and 'Lightning' during the summers of 1868, 1869 and 1870, under the scientific direction of Dr. Carpenter, J. Gwyn Jeffreys, and Dr. Wyville Thomson. Porcupine (Ship); Lightning (Ship); Ocean; Marine animals; Deep-sea temperature; Marine sediments. 240 THE DEPTHS OF THE SEA. [chap. VI. suitable for scientific purposes. Tiie oyster dredge has a scraper only on one side. In the skilled hands of the fishermen this is no disadvantage, for it is always sent down in such a way that it falls fa
. The depths of the sea; an account of the general results of the dredging cruises of SS. 'Porcupine' and 'Lightning' during the summers of 1868, 1869 and 1870, under the scientific direction of Dr. Carpenter, J. Gwyn Jeffreys, and Dr. Wyville Thomson. Porcupine (Ship); Lightning (Ship); Ocean; Marine animals; Deep-sea temperature; Marine sediments. 240 THE DEPTHS OF THE SEA. [chap. VI. suitable for scientific purposes. Tiie oyster dredge has a scraper only on one side. In the skilled hands of the fishermen this is no disadvantage, for it is always sent down in such a way that it falls face foremost; but philosophers using it in deep w^ater very generally found that whether from clumsiness or from want of sufficient practice, they had got the dredge down on its back, and of course it came up empty. Again, oyster dredgers are only allowed to take ovsters of a certain. size, and the meshing of the commercial dredge is so contrived as to allow all bodies under a certain considerable size to pass through. This defeats the object of the naturalist; for some of the prizes to which he attaches the liio'hest value are mites of things scarcely visible to the unaided eye. The remedy for these de- fects is to have a scraper on each side, with the arms attached in such a way that one or other of the scrapers must reach the ground in whatever position the dredge may fall; and to have the bag deeper in proportion to the size of the frame, and of a material which is only sufficiently Fia. 45.—' Ball's Dredge.'. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, C. Wyville (Charles Wyville), Sir, 1830-1882; Carpenter, William Benjamin, 1813-1885; Jeffreys, John Gwyn, 1809-1885. London, Macmillan and co.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectmar, booksubjectocean
