12 
Fig. 10. 
Sounding 
Lead with 
Stellwagen 
Cup.  (Sigs- 
bee.) 
THREE CRUISES OF (HE “ BLAKE." 
the hemp-line soundings by the great diminution of speed in the 
running out of the rope after the sinker has struck, 
but by the instantaneous action of the sinker on the 
wire when striking bottom ; the wire stops, and in 
less than a second the momentum of the reel is 
checked by the friction-rope attached to it. The 
dropping of the shot is detected on deck with as 
great certainty as if it had been followed by the eye 
to the very bottom ; indeed, the percentage of error 
in soundings made with piano-wire is probably not 
more than one fourth of one per cent. The error in 
soundings made by the old methods can only be de- 
termined after the rope-soundings have been corrected 
by wire-soundings. To those who are not familiar 
with the practical working of deep-sea soundings as 
formerly carried on, a fect figures enabling them to 
compare the old with the new methods may be inter- 
esting. In the “ Challenger” the 
deep-sea soundings were made with Lo) f o 
a rope of eight tenths of an inch pj. 9, — Comparative 
in circumference, nearly as large as m. PE ad BEA 
the steel-wire rope which we used ing. (Sigsbee.) 
in dredging, and having a breaking weight of 1,200 
pounds. The time occupied in lowering the sound- 
ing machine and its weights, often more than 300 
pounds, was three to four times as great as on the 
* Blake." We employed a steel wire АМ о. 20, Amer- 
ican gauge), with breaking weight of 240 pounds, 
weighted for the deepest soundings only, with a sixty- 
pound shot. The time required to reel in with Cap- 
tain Sigsbee’s wire machine was generally below one 
minute and a half per one hundred fathoms, some- 
times not more than fifty seconds, while the time re- 
quired to strike bottom averaged from fifty to seventy- 
five seconds per one hundred fathoms in the deepest 
soundings up to two thousand fathoms. In depths 
less than one thousand fathoms or so, an ordinary 
thirty-four pound lead with a Stellwagen cup for ob- 
aining bottom specimens was used. "he lead was reeled in 
t g bott p d. The lead led 
