CHAP. V.] THE GULF-STREAM. 395 
through the bread-bag during the progress of the dredge to the 
surface; and this made it all the more remarkable that no ani- 
mal higher in the scale than a rhizopod was contained in the 
dredge. | 
A series of temperature soundings were taken at intervals of 
50 fathoms down to 700 fathoms (see Table— Appendix A 
to this chapter), and a second series to a depth of 150 fathoms 
at closer intervals gave the following results: 
Sulacesean sain eel 20 sO. 100;fathoms 4 seas ee ocaole: 
BAU aAtHOMIS..: 5... <. +. 19 “6 1) Nek en aes int me i fs 
OMY oo ctecn eset Le 0 10 See Aare i err Wee sh 
1) “SCOR, See Me TS OpOR Se), ee MRR 
BNI rstc cote sas a oce ESO 
While the dredge was down, observations were made on the 
direction and force of the currents at the surface and at differ- 
ent depths below it. The surface-current can usually be de- 
termined without any great difficulty; indeed, we get at all 
events a rough approximation to its determination, in the dif- 
ference at the end of a given time between the position of the 
ship by observation and her position by dead reckoning. In 
fine weather, however, the surface-current may be determined 
much more exactly. When the dredge is well on the bottom, 
one of the quarter-boats is lowered and anchored to the dredge- 
line, the line between the boat and the ship being kept slack, 
and the ship drifting away. The boat thus becomes a fixed 
point, and from it a current-log is run out, the log-ship consist- 
ing of a triangular piece of wood weighted at the apex, and 
kept at the surface by an oar lashed across its base. The log- 
line is marked to fathoms, and is allowed to run for a given 
time, say six or twelve minutes; the line is then checked, and 
the bearing of the log-ship taken from the boat, which gives 
the direction of the current; while the number of fathoms run 
out multiplied by the proportion which the time of running 
bears to an hour gives its hourly rate. 
