304 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
Sea (England, Norway, Denmark, Germany, and Holland) established 
the ‘‘Permanent International Council for the Exploration of the 
Sea,”’ with a central laboratory at Christiania. 
Oceanographic studies are of two kinds, one physico-chemical, the 
other biological. The first includes the determination of the depth 
of the sea bottom and the study of the bottom; determination of 
the temperature, the salinity, the gaseous contents of the sea water, 
the color and transparency of the water, and finally the study of 
currents. These investigations require the use of special instruments, 
involving a technique the details of which it is impossible to enter 
into here. It is enough to say that several of these operations take 
place at the same time. Thus, when a sounding is made and a speci- 
men of the bottom secured at the point sounded, the temperature is 
observed and specimens of the water at various depths taken. 
The biological investigations pertain to all organisms both animal 
and vegetable which pass their existence in the seas; to their evolution, 
to their distribution, etc.: they are specially concerned with the ex- 
tremely varied organisms which move actively or float passively in 
the superficial layers, and which constitute the so-called plankton,} 
a name we commonly reserve for the organisms of very small size 
which often swarm at the surface, in differentiation from the animals 
of large size like the fishes which inhabit the same regions; to the 
former class we sometimes give, in contradistinction, the name of 
microplankton. 
The attributes of water with which oceanography is concerned above 
all are temperature, because of its biological importance; salinity, 
thanks to which it is possible to determine the geographical origin 
of the sea waters; and the density, which depends on the two pre- 
ceding and on the pressure, and which is related directly to the circu- 
lation of the water, as much in the vertical sense as in the horizontal. 
The color and transparency are less important, though not negligible, 
for they help to better define the biological complex in which the 
plankton is evolved. 
In order to capture the plankton organisms, as well as the animals 
swimming at different depths, nets much varying in form and dimen- 
sions are used, of which some can be closed at any desired depth; 
for the animals which live permanently on the bottoms, recourse is 
had to trawls or dragnets of different types. All these oceanographic 
operations require on board the vessel from which they are per- 
formed a special equipment of winches, cables, drums, and booms, 
for the immersion and recovery of the large nets. 
In founding the ‘‘Permanent International Council for the Explo- 
ration of the Sea,’”’ the nations bordering on the North Sea consid- 
1 From zdayxréc, wandering, vagabond. 
