ON PLANKTON AND PHYSICAL CONDITIONS OF ENGLISH CHANNEL. 445 
As the year’s collections are not yet complete, the Committee confines its 
report on the present occasion to a description of the methods and apparatus 
employed, and hopes to present a final report at the Bradford meeting. 
The route fixed for the Survey consisted of the following lines :— 
(1) from Plymouth to Ushant, with stations in mid-Channel (50 fathoms) 
and off Ushant (60 fathoms) ; (2) from Ushant in a westerly direction 
towards the 100-fathom line, with a station near Parson’s Bank (75 
fathoms) ; (3) from Parson’s Bank northwards towards Mount’s Bay, with 
a station in 50 fathoms ; (4) from Mount’s Bay to Plymouth, 
The hydrographic apparatus employed consisted on all occasions of 
Negretti and Zambra’s Deep-sea Reversible Thermometers, and of one of 
Dr. Mill’s Water Bottles. Complete series of temperatures were taken on 
all occasions. 
On the February cruise the biological apparatus consisted of a number 
of silk-gauze nets of various meshes for surface collections and of a semi- 
rotary hand-pump and 40 fathoms of armoured hose (having a diameter 
of one inch) for quantitative samples both of surface and deep-water 
plankton. Accessory apparatus for filtermg the plankton and measuring 
the volume of water filtered was also provided. 
The results obtained by pumping appeared to be quite satisfactory for 
quantitative determination of the more immobile elements of the plank- 
ton, such as diatoms and even the smaller copepods ; but the vertical 
distribution of the plankton was found to be so variable, under the varying 
influence of darkness and light, even at a depth of 40 fathoms, that the 
length of hose, which alone was obtainable with the means at the Com- 
mittee’s disposal, was inadequate to provide a proper series of samples for 
comparative purposes in cases where the depth exceeded 50 fathoms. 
On returning from this cruise, therefore, Mr. Garstang determined to 
attempt a solution of the difficulties which have hitherto invested the 
problem of a simple but efficient opening and closing net for horizontal 
towing ; as well as to construct a vertical net, after Hensen’s pattern, for 
comparative estimation of the total quantity of plankton present at 
different places and at different seasons. 
These nets were ready for use towards the end of May, and were 
employed with perfect success during the May and September cruises. As 
the closing net has proved to be a thoroughly reliable instrument, the 
principles of its construction are here briefly given, and the net itself will 
be exhibited and tried at sea during the Dover Meeting. (The trials took 
place on September 17 on board Mr. J. W. Woodall’s yacht Vallota, in 
the presence of Sir John Murray, Mr. H. N. Dickson, and Mr. I. C, 
Thompson, and were completely successful.) 
The principal obstacles to the use of closing nets for horizontal towing 
at definite depths have been (1) the tendency of the net to oscillate, 
during towing, through a thick stratum of water, depending on inevitable 
variations in the rate of towing ; (2) the uncertainty of determining the 
actual depth of the net at any moment, owing to the curvature of the line 
produced by the resistance of the water ; (3) the difficulty of ensuring the 
proper opening and complete closure of the net at the depth required. 
It appeared that the first and second obstacles might be overcome by 
combining a minimum resistance of the towing line and net with a 
maximum weight of the net frame. The net was therefore designed to be 
towed by fine steel wire instead of a hempen line, and provision was made 
for a heavy net frame to support a small net, as well as for the voluntary 
