Besides the meteorological observations and the collection of
plankton -- in fine silk tow-nets -- the investigations consisted
of taking temperatures and samples of water at different depths The
temperatures below the surface were ascertained by the best modern
reversing thermometers (Richter's); these thermometers are capable
of giving the temperature to within a few hundredths of a degree at
any depth. Samples of water were taken for the most part with Ekman's
reversing water-sampler; it consists of a brass tube, with a valve at
each end. When it is lowered the valves are open, so that the water
passes freely through the tube. When the apparatus has reached the
depth from which a sample is to be taken, a small slipping sinker
is sent down along the line. When the sinker strikes the sampler,
it displaces a small pin, which holds the brass tube in the position
in which the valves remain open. The tube then swings over, and this
closes the valves, so that the tube is filled with a hermetically
enclosed sample of water. These water samples were put into small
bottles, which were afterwards sent to Bergen, where the salinity of
each sample was determined. On the first cruise, in June and July,
1910, the observations on board were carried out by Mr. Adolf Schroer,
besides the permanent members of the expedition. The observations
in the South Atlantic in the following year were for the most part
carried out by Lieutenant Gjertsen and Kutschin.

The Atlantic Ocean is traversed by a series of main currents, which
are of great importance on account of their powerful influence
on the physical conditions of the surrounding regions of sea and
atmosphere. By its oceanographical investigations in 1910 and 1911
the Fram expedition has made important contributions to our knowledge
of many of these currents. We shall first speak of the investigations