336 APPENDIX. 



The temperature at various depths is correctly ascertained by a very 

 clever thermometrical contrivance, which is difficult to be explained with- 

 out the presence of the instrument itself, or a diagram in illustration 

 thereof. Strange to say at the greatest depth the water is found to bo 

 intensely cold, which is supposed to be owing to an under stratum of cold 

 water, perhaps a condensed polar current. May not the extreme con- 

 densation of the liquid element at such a depth be alone accountable for 

 this degree of cold. The pressure must be enormous. Sometimes the 

 thermometers in spite of the strong enclosure and the equable bearing of 

 the water, are shivered into fragments. A strong metal tube was shown 

 which had enclosed a thermometer, that in consequence of an unobserved 

 defect when put overboard, on coming again to the surface was found to 

 have suffered a complete collapse, the thermometer entirely destroyed. 

 Accidents like these are inseparable from all such services, and operate 

 as cautions to prevent their recurrence. The sinker, about 400 lbs. 

 weight, attached to the sounding line, and calculated to carry it to any 

 depth, resembles an Armstrong shell, bored lengthwise. It is fitted 

 with a mechanical contrivance projecting from it about eighteen inches, 

 a tube, which on reaching the bottom, having collected a portion of its 

 material, is forced upward through the sinker, which then immediately 

 becomes detached, and is left behind. Every time that deep sound-* 

 ings are taken the Challenger drops one of these as a memento of 

 her visit. The line is recovered by the aid of a donkey engine of consid* 

 erable power, which yet has sometimes to be assisted by urging the ship 

 backward or forward, as may be expedient. 



The dredging apparata is larger or smaller according to the depths. 

 It is a strong net with an iron frame and open mouth, and drags along a 

 trail composed of a broad swab of loose ropes, which Professor Thompson 

 informed the party was very useful in collecting material which had 

 been passed or loosened by the dredge itself. Every mechanical facility 

 is taken advantage of in paying out the line, both in sounding and dredg* 

 ing. The reels are fastened to the waists of the ship, and the large 

 quantity of rope wound on them attested to the great depth already 

 reached, and to the provision for finding at the " lowest depth" " a lower 

 deep." 



It is remarkable that at the deepest soundings, animal organisms are 

 found ; zoophytes, and sponges, but nothing of a vegetable nature. At* 

 depths of four to five hundred fathoms, crustaceans of remarkable form 

 have been dredged, new in type, without eyes, but with processes ex- 

 tending from the head which may make the sense of feeling very acute. 

 Some of these of a pale pink colour when captured, were changed by the 

 light to a yellowish white — and alcohol absorbed all colour. 



After the sounding and dredging gear had been looked over, the 

 divisions of the ship set apart for the labours of the Scientists of the exhi* 

 bition, were visited — the chemical department, the photographic and 

 natural history departments. Several of the Professors were absent in 

 Canada ; but the interest was well sustained by the kindness of Professor 

 Wyville Thompson, who opened up the wonders of the great deep to the 

 observation of all who chose to take pleasure in them. The blind crus^ 



