Page:The American Cyclopædia (1879) Volume VI.djvu/266

 258 DREDGING (DEEP-SEA) hooks of galvanized iron were hinged inside the bulwark in such a way that they could be turned flat against the latter when not in use. It is not usually practicable to pay out so large a surplus of line in deep casts as in more moderate ones. It is therefore well to attach a heavy weight to the line at a considerable distance above the dredge, say a fifth or a sixth of the depth ; thus the traction on the dredge will be nearly horizontal. Another good prac- tice in very deep casts is to steam slowly to windward during the descent of the dredge until the dredge rope is nearly perpendicular, and then let the vessel drift with the wind or cur- rent. The motion is thus communicated to the weight from the vessel, and the dredging per- formed as if from that and not from the latter. The contents of the dredge will generally be found to consist of mud or sand, out of which the specimens are to be sorted. For this a graduated set of sieves is used, constructed so as to fit in one another, the coarsest on top. The mud being placed in the latter, the whole set is moved up and down in a tub of water, after which the specimens can be selected with ease. The best mode of preserving them is to put them in alcohol, the more delicate ones in bot- tles, the coarser ones in bags of muslin or bun- ting, which can be accumulated in larger vessels. Some very delicate objects, which are liable to lose their shape in pure alcohol, can be pre- served successfully in a mixture of alcohol and glycerine. Superfluous duplicates of inollusks, Crustacea, echinoderms, corals, and sponges can be preserved by drying. Care must be taken not to place colored horny sponges in the same vessel with other specimens, as they are apt to stain everything as with ink. Abundant samples of the sand or mud ought to be pre- served, as they afford an immense variety of microscopical specimens of great value. An erroneous opinion prevails that the late Ameri- can and English expeditions first revealed the existence of an abundant deep-sea fauna. The late Edward Forbes asserted that life becomes less and less as we descend, until it is almost or utterly extinguished. Guided by his own researches in the Mediterranean, he placed the limit of life at the very moderate depth of 200 to 300 fathoms. Norwegian fishermen', from time immemorial, have taken certain fishes in depths of 100 to 300 fathoms. Some of these are quite large, as the halibut and the ling, and some have never been obtained in lesser depths. On the coast of Portugal also the fish- ermen of Setubal fish in similar depths for a peculiar shark, using lines of 500 fathoms. It is evident that where such fishes can live they must find abundant food, and this was proved by the contents of their stomachs, and by the specimens occasionally brought up on the hooks, but mostly rejected with superstitious dread by the fishermen. The Scandinavian naturalists Lov6n, Sars, Danielssen, Koren, and others, made extensive researches by means of the dredge in depths of 200 to 300 fathoms, bringing to light a great variety of animal forms peculiar to that region. Sir John Ross relates in his "Voyage," published in 1819, that in the preceding year he obtained a sound- ing in Baffin Bay in 1,000 fathoms, and brought up with the lead mud containing worms, and a living star fish (astrophyton) attached to the line. Sir James C. Ross, in his voyage to the antarctic regions in 1839-'43, obtained with the dredge in 270 fathoms " an abundance and great variety of animal life." He says : " Con- trary to the general belief of naturalists, I have no doubt that from however great a depth we may be able to bring up the mud and stones of the bed of the ocean, we shall find them teem- ing with animal life. The extreme pressure at the greatest depth does not appear to affect these creatures ; hitherto we have not been able to determine this point beyond 1,000 fath- oms, but from that depth several small fish have been brought up with the mud." At a later time evidences of the existence of animal life at great depths began to accumulate. Eh- renberg showed in 1851 that foraminifera from a depth of 2,000 fathoms still contained un- changed animal matter. Prof. Bailey of West Point confirmed these observations, although differing in the explanation of the fact. In 1853 the soundings of the United States coast sur- vey revealed for the first time the great fora- minifera bed which almost unmixed covers a large extent of the ocean floor. In a sample of scarcely two cubic inches, from a depth of 510 fathoms, Mr. Pourtales found specimens or rec- ognizable fragments of at least 48 species, 20 of them mollusks. Dr. Wallich, accompanying the sounding expedition of Sir L. McClintock to Greenland, obtained living animals from depths of 1,000 to 2,500 fathoms, among them star fishes of considerable size. Doubt was still thrown on these results from the fact that some foraminifera are found floating near the surface, and it was even objected that the star fishes might have been swimming when entan- gled in the line. No such objections could be made to the observations of Dr. Allman and A. Milne-Edwards, who found oysters and other shellfish, worms, and corals on a telegraph ca- ble raised from a depth of 1,000 to 1,400 fath- oms in the Mediterranean ; or to the results of the Swedish expedition to Spitzbergen, under Thorell, who obtained, partly by dredging and partly by means of the Bulldog machine, ex- tensive collections from depths down to 1,400 fathoms. In 1868 Prof. Sars of Christiania published a list of 427 species of animals living in depths of 200 to 300 and even as much as 450 fathoms. In the United States, dredging up to a recent date has received but little at- tention. The most successful worker in that field has been the late Dr. W. Stimpson, who however confined himself to quite moderate depths. In 1867 Professor Peirce, superinten- dent of the coast survey, commissioned Mr. Pourtales, one of his assistants, to make some dredgings in connection with the sounding out