The cruise of Her Majesty's ship "Challenger" : voyages over many seas, scenes in many lands . es the sounding-platform, it isremoved, and the results are carefully readoff. The temperature is then taken fromthe surface to 700 fathoms in the same man-ner. Sometimes it is considered necessaryto obtain temperatures at every 10 fathomsfrom the surface to 200 fathoms, and atevery 50 fathoms to 600 or 700 fathoms;this, of course, considerably increases the time occu-pied in obtaining these observations. When the whole of the soundings and temperatureobservations have been obtained between any twopl
The cruise of Her Majesty's ship "Challenger" : voyages over many seas, scenes in many lands . es the sounding-platform, it isremoved, and the results are carefully readoff. The temperature is then taken fromthe surface to 700 fathoms in the same man-ner. Sometimes it is considered necessaryto obtain temperatures at every 10 fathomsfrom the surface to 200 fathoms, and atevery 50 fathoms to 600 or 700 fathoms;this, of course, considerably increases the time occu-pied in obtaining these observations. When the whole of the soundings and temperatureobservations have been obtained between any twoplaces, a plan is drawn showing the section of thebottom and isothermal lines at different depths. For the purpose of dredging in deep water, threedifferent-sized ropes are supplied, of 2, 2^, and3 inches in circumference. Each rope is spliced so 54 CEUISE OF CHALLENGER. as to form one continuous length of 3000 to 4000fathoms, and is kept coiled away in a large rack,conveniently situated for use. These lines aremarked at each 100 fathoms in the same manner asthe sounding-line. Fig. The dredges (Fig. 9) supplied consisted of an ironframe, and were of three sizes, 5, 4, and 3 feet inlength, and from 15 to 9 inches in width. The ironframe, to which was secured the bag or net, is in-tended to skim the surface of the bottom, and the APPARATUS AND APPLIANCES USED. 55 Fig. 10. net to catch and retain all that might come in itsway ; at the bottom of this bag a number of hempenswabs were generally secured so as to sweep alongand bring up small animal life,coral, sponges, &c. These dredgesafter a time were set aside and re-placed by the ordinary beam trawlused in shallow water around ourown coast. The operation of dredging ortrawling, like that of sounding, iscarried on from the mainyard, thedredge rope being rove through aniron block which is attached to theaccumulator in the same manner asdescribed for sounding. For this operation it is neces-sary to use a much larger accu-mul
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Keywords: ., bookcentury180, bookdecade1870, booksubjectvoyagesaroundtheworld
