DEEP-SEA EXPLORATION. 
311 
[Correction table. Tanner reel. Wire No. 21. Music No. 17, A. W. G.] 
Turns on 
Tanner 
reel. 
Fathoms 
1>.V 
measur- 
ing reel. 
Correc- 
tion, in 
fathoms. 
Turns on 
Tanner 
reel. 
Tathoms 
by 
measur- 
ing reel. 
Correc- 
tion, in 
fathoms. 
Turns on 
Tanner 
reel. 
Fathoms 
i>y 
measur- 
ing reel. 
Correc- 
tion, in 
fathoms. 
2.5 
25 
0 
25 
227 
2 
25 
432 
7 
50 
50 
0 
50 
252 
2 
50 
458 
8 
75 
75 
0 
75 
278 
3 
75 
484 
9 
10(1 
101 
1 
300 
303 
3 
500 
510 
10 
25 
126 
1 
25 
329 
4 
25 
536 
11 
50 
151 
1 
50 
354 
4 
50 
562 
12 ■ 
75 
176 
1 
75 
380 
5 
200 
202 
2 
400 
400 
r> 
The wire is in one piece, without splices, having been made to order l>y Washburn & 
Moen. 
Example: A sounding is made, the register reading 425 turns. What is the depth 
in fathoms? 
Number of turns on tlie reel .550 cor. + 12 
Number of tarns registered 425 
Turns remaining on reel 125 cor. — 1 
Correction for 425 turns 4-11 
Number of turns registered 425 
Depth in fathoms 436 
SIR WILLIAM THOMSON’S MACHINE FOR SOUNDING WITH WIRE. 
Plate XVIII showing the Thomson machine as it was used on board the Blalce 
for one season and the description of its operation,, the latter in the words of the 
inventor, are taken from Sigsbee’s Deep-Sea Sounding and Dredging (page 54). It is 
shown here not only as the first successful apparatus for sounding with wire, but as a 
type of the simplest and most easily constructed sounding machine. Sir William 
describes the machine and its action as follows: 
The wire is coiled on a large wheel (of very thin sheet-iroir galvanized) which is made as light as 
possible, so that when the weight reaches the bottom the inertia of the wheel may not shoot the wire 
out so far as to let it coil on the bottom. The avoidance of such coiling of the wire on the bottom is 
the chief condition re(|uisite to provide against the possibility of kinks, and for this reason a short 
piece of hemp line, about live fathoms in length, is interposed between the wire and the sounding 
weight, so that, although a little of the hemp line may coil on the bottom, the wire may be quite 
jirevented from reaching the Itottom. 
A galvauized-iron ring of about half a pound weight is attached to the lower end of the 
wire, so as to form the coupling on the junction between the wire and the hemp line, and to keep the 
wire tight when the lead is on the bottom and the hemp line is slackened, dhe art of deep-sea sounding 
is to put such a resistance on the wheel as shall secure that the moment the weight reaches the bottom 
the wheel will stop. By the “moment” I mean within one second of time. Lightness of the wheel is 
necessary for this. 
A measured resistance is applied systematically to the wheel, always more than enough to balance 
the weight of wire out. The only failure in deep-sea soundings with pianoforte wire hitherto made 
has been owing to neglect of this essential condition. The rule adopted in )>ractice is to apply 
resistance, always exceeding by 10 pounds the weight of the wire out. Then the sinker l)eing ,34 
pounds, we have 24 pounds weight left for a moving force. That, I have found, is amjily sufficieut to 
