SEA-FISHERIES LABORATORY. O87 
the @ for the net, with, however, a narrow mouth instead 
of its normal wider one. Having found this, a series of 
catches are made under good weather conditions with the 
same net, first with the narrow mouth and then with the 
wider mouth. If now the average volume of catch with 
the narrow mouth is reduced to the volume under the 
square metre of surface, by application of the coefficient 
g, it is easy to find what coefficient is necessary, to bring 
the actual observed volume caught by the wide mouthed 
net, up to the same volume under the sq. metre. The 
new coefficient corrected for the variation due to pressure 
d, is termed wp. 
This implies, of course, a uniform distribution in the 
water whilst the series of catches was made. 
For conical nets the procedure is practically the 
same, though the formulae are somewhat different. If a 
firm plate is pulled through the water with the surface 
perpendicular to the direction of pull, there will be a 
pressure from before and a pull from behind which, added 
together, cause a tendency to bend. If the plate is 
funnel-shaped, the pulling force z is divided into two 
components (parallelogram of forces), one, z cos a is 
applied in the direction of the funnel wall and the other, 
2sin ais applied perpendicular to it. The apical angle in 
the funnel is 2a. 
The conical net exhibits such a funnel, except that 
its walls are permeable. The pressure d is assumed as 
before to be uniform all over the net, the correction for 
this to be made approximately or empirically as described 
above. 
Now, if vs) is the speed at which the net is hauled, 
the pull component on the outer net wall is not s.sina 
because under the influence of the pressure d the current 
w(d) streams out of the net, and this is accelerated by this 
