148 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
To use the apparatus, prepare it as in fig. 1, plate 11, lower it vertically to the proper 
point, and tow it slowly through the water, veering and heaving in on the tow line in 
order to maintain the desired depth, which can be determined within a few fathoms 
by the dredging quadrant, an instrument in constant use on board the Albatross. 
To recover it, stop and back until the tow rope is vertical, heaving in sufhcient 
line during the operation to keep the net at the proper depth; then send the messenger 
down to act on the friction clamp, release the tripping lines, and close the lower part 
of the net as shown in fig. 0. 
The net may be run up to the surface at any desired speed, the upi>er portion 
taking in anything it encounters en route, while the lower i)art remains closed against 
even the most minute forms. 
The messenger is in two parts, which, having been i)laced around the tow rope, 
are seized together with marline. It sinks at the rate of about 050 feet per minute, 
and the impact can usually be distinctly felt by taking hold of the tow line. 
This apparatus was used successfully to a depth of 1,700 fathoms, yet I looked 
upon it as a makeshift; the heavy sinker on the lower bridle caused the net to tow at 
a considerable angle, thus diminishing the useful area of the ring. An improved form 
of intermediate tow net was subsequently devised by the writer, in which fully three- 
fourths of the area of the ring does useful work. The apparatus is simplified, and its 
action more direct and certain. 
THE TANNEE INTERMEDIATE TOW NET, IMPROVED PATTERN. 
This apparatus is composed of a brass frame carrying a net so arranged with 
drawsti'ing, movable weights, messenger, friction clamp, and tripping lines, that the 
lower part can be closed at will. Its construction may be readily understood by 
reference to idate 12 and the following explanations: 
A. A. Ring : I)rass pipe. 
B. B. Arms: brass pipe. 
C. C. C. C. Legs: brass pipe. 
D. Apron: sheet brass. 
E. E. E. E. Apron bolts: brass. 
Tees, for arms and legs: brass. 
F. F. F. F. Blocks, for drawstring: brass. 
G. G. Weights for drawstring : lead. 
H. Sinker: cast iron; wrought links. 
I. Friction clamp: frame, brass; tum- 
bler, steel. 
K. Messenger: cast iron. 
L. Wrench: steel. 
Net: q-inch mesh. 
First lining: mosquito net (for whole net). 
Second lining: silk gauze (for lower half). 
Guide-rings: brass. 
N. Drawstring: braided cord. 
O. Lashing: cod line, cotton. 
M. Tripping-linos: codline, cotton or flax 
General description . — Tlie ring is 2 feet 5 inches inside diameter, composed of 
brass pipe Ij-g inch outside diameter, bent in a circular form, the ends joined by a 
union. On the ring are four tees, two on each side, spaced 6 inches apart, and secured 
in place. The half of the ring opposite the union is filled with lead, which gives it a 
preponderance of about 10 pounds. 
The arms are of brass pipe of the same diameter as the ring; the lower ends are 
screwed into tees which move freely on the ring between those above mentioned, the 
upper ends having a hinge joint held in place by the shackle pin. 
The legs, four in number, are also of brass pipe, j-l of an inch outside diameter 
and 5 feet 5^- inches total length, with net length (from lower side of ring to apron) 5 
