368 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
In preiiariug the net for use it is advisable to lasb the lining separately as near 
the end as practicable and place it inside of the net, lashing the end of the latter in 
such a manner that the former \yill rest entirely upon it, relieving the more delicate 
material from the strain of towing; otherwise it will be ruined by the great volume of 
water passed through it. It is towed from the swinging boom at about 2 knots per 
hour, and, when the vessel is engaged solely in surface collecting, two nets are used 
at the same time, one at each boom. 
TOW NETS FOR INTERMEDIATE DEPTHS. 
A large tow net was devised by the writer, at the instance of Professor Baird, for 
the purpose of taking fish at the surface and at intermediate depths. It was used for 
the first time on May 8, 1883. 
The ring was made of 1-inch round iron, and was 10 feet in diameter; the net, 
1-inch mesh and 20 feet in length; the bridle had four legs, which were seized at equal 
distances around the ring, and the steel-wire dredge rope was used as a tow line. 
This apparatus was towed at various depths, from surface to bottom, at sjieeds 
ranging from 2 to 7 knots per hour, but it failed utterly in so far as the caiiture of 
pelagic forms was concerned; any fish which had sufficient celerity of movement to 
escape a beam trawl would avoid this net. The trouble seemed to arise from its 
^‘firing,” lor when used at night its tracks several fathoms below the surface could be 
distinctly seen. On one occasion, when a school of mackei'el was attacked with it 
on a dark night, we could see the mass separate only a few feet in advance and then 
promptly close again in its rear, and not one was caught. The school was so dense 
that it seemed impossible to drag so large a net among them without catching one or 
two at least; but after an hour or more of towing in every direction at varying speeds 
from 1 to 8 knots, without the capture of a single specimen, we gave it up as a failure. 
Surface tow nets attached to the dredge rope were used on board the ChaUenger 
for intermediate collecting, but a knowledge of the depths at which the specimens 
were secured was still lacking. The same practice was followed on board the Fish 
Rawlc until we imiiroved upon it by adopting wing nets, which Avere attached to each 
end of the trawl beam, and performed the functions of collectors from surface to 
bottom, and thence to the surface again. They Avere like an ordinary surface tow net 
with a pocket added. The material was cheese-cloth, and being much finer than any 
portion of the trawl which they accompanied, they usually contained a miscellaneous 
collection of small forms, many of which Avould not have been secured by any other 
method in practice at that time. Of course, we had little knowledge of the depths at 
AAhich the various forms Avere secured. Such as were common to both Aving net and 
surface net Avere, in a general Avay, assigned to areas within the influence of sunlight, 
Avhile those found in the Aviug nets alone Avere allotted to depths more profound. 
THE TANNER INTERMEDIATE TOAV NET, FIRST FATTEEN, 
This net (plate xxxvi) Avas improvised at sea from materials at hand after the 
failure of other apparatus. Its iiurpose is to collect animal life from known inter- 
mediate depths, and although it has been superseded by a later pattern it is repro- 
duced as a guide to others who may Avish to construct a similar net Avith the slender 
resources usually available on shipboard. 
The ring a is of brass, 2 feet 9 inches in diameter, Avith a four-legged bridle ft, 
secured to eyes s^iaced at equal distances around it and shackled to the loAver link of 
