296 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
2. That part of the lip of the tunililer on which the hail of the shot rests shoulil have the edges 
beveled or rounded, otherwise the edges may he broken up and spread, thus preventing the tunilder 
from l)eing thrown hack between the side pieces. Thin washers put on either side of the tumbler and 
pawl wouhl probably be an imjirovement. 
3. All parts should work freely. 
4. The bottom of the siiecimeu cup should have the proper bevel; if too sharp it may retain but 
a small specimen, and if too blunt the rod may not penetrate firm material. 
5. The spiral spring h should not be so strong as to prevent soft bottom material entering the 
cup; its strength should be suflicient, when the rod is lying Hat, to force the valve smartly to its 
seat when the valve is pushed inward and released, and j^et not strong enough to seat it by about 1 
inch, when the rod is held bottom upwards. The springs for the Blake’s rods are of No. 17 American, 
orNo. 18 Stuhb’s gauge sjiring-brass wire; they are 3 inches in length when not under compression, 
and have twelve coils each. Any spring thus made could easily he adapted to the reijuirements. 
6. If desired, the rod might be made considerably lighter for very dee]) work, the present size of 
the detacher being retained. On the scale of plate xvi, the rod and detacher are strong and handy, 
weighing pounds. The size of the specimen sought should have much iuiliience in determining 
the size of the rod. If only an indication of the bottom material were wanted, no specimen for 
careful examination being needed, a rod weighing only 2 or 3 pounds would suffice. 
DETAILS OF CONSTRUCTION. 
The cylinder a, fig. 1, plate xyi, is a brass tube of commercial pattern, 2^ inches 
outside diameter and 10 inches in length, rigidly secured to the perforated plate j by 
small brass screws, and the valve seat e is soldered to the other extremity of the 
cylinder winch has its cutting edge sharply beveled as shown in fig. 1. The ])oppet- 
valve f is of cast brass secured by a drift-jiin to its hollow stem, a thin brass tube, 
which im])inges on the spiral spring h, both traversing the stem freely. The upper and 
lower guide stem is a brass casting enlarged near its center to form the perforated 
Xdate j. The hollow cone i is a brass casting having apertures, p, for the escape of 
water; the cylindrical ring d is soldered to its base. 
The detacher is composed of the tumbler m, pawl I, swivel I', and spring all 
movable parts Avorking on loose lirass pins Avhich are held in place by small split keys 
of spring brass. The spring is of No. 14 American gauge brass spring wire. The 
detacher frame is riveted to the flattened end of the guide stem, in prolongation of it, 
and there is a screw joint at h, on the cylinder, by which the two x>iii'ts are seiiarated 
for convenience in securing its contents. 
TO USE THE SOUNDING-ROD. 
To sound and liring up a specimen of the bottom, attach the stray line, which 
should always intervene between the wire and sounding rod, to the swivel ring Z-, x)ass 
the rod through the hole in the sinker, hook the wire bail r over the li}i of the tumbler 
w, lock the x>aivl and tumbler and susiiend the rod from the swivel ring A', when it will 
liromiitly assume a vertical position. The cone i remains unseated during its descent 
by contact with the shot (fig. 1), and the valve/ is raised by the uiiward ju'essure of 
the water, which then circulates freely through the cylinder, reducing its resistance 
and iTicreasing its rate of descent. 
When the sinker strikes the bottom the tension on the line is relieved and it 
becomes more or less slackened, the pawl assumes a horizontal jmsition by its own 
weight, releasing the tumbler, Avhich is thrown out of action by the sxiring n, assisted 
by excess of weight at the li]>, and thus the sinker is released. 
The combined weight of shot, sounding-rod, small lead, and thermometer, alto- 
gether about 70 pounds, descending at the rate of S to 10 feet per second, forces the 
