Between the two long lines of section there is a distance of between ten and fifteen degrees of latitude.  There is, therefore, a considerable difference in temperature.  In the southern section the average surface temperature at Stations 1 to 26 (June 17 to July 17) was 17.9deg.  C.; in the northern section at Stations 36 to 60 (July 26 to August 19) it was 21.6deg.  C. There was thus a difference of 3.7deg.  C. If all the stations had been taken simultaneously, the difference would have been somewhat greater; the northern section was, of course, taken later in the winter, and the temperatures were therefore proportionally lower than in the southern section.  The difference corresponds fairly accurately with that which Kr:ummel has calculated from previous observations.

We must now look at the conditions below the surface in that part of the South Atlantic which was investigated by the Fram Expedition.

The observations show in the first place that both temperatures and salinities at every one of the stations give the same values from the surface downward to somewhere between 75 and 150 metres (40.8 and 81.7 fathoms).  This equalization of temperature and salinity is due to the vertical currents produced by cooling in winter; we shall return to it later.  But below these depths the temperatures and salinities decrease rather rapidly for some distance.

The conditions of temperature at 400 metres (218 fathoms) below the surface are shown in the next little chart.  This chart is based on the Fram Expedition, and, as regards the other parts of the ocean, on Schott’s comparison of the results of previous expeditions.  It will be seen that the Fram’s observations agree very well with previous soundings, but are much more detailed.

The chart shows clearly that it is much warmer at 400 metres (218 fathoms) in the central part of the South Atlantic than either farther north —­ nearer the Equator —­ or farther south.  On the Equator there is a fairly large area where the temperature is only 7deg. or 8deg.  C. at 400 metres, whereas in lats. 2Odeg. to 30deg.  S. there are large regions where it is above 12deg.  C.; sometimes above 13deg.  C., or even 14deg.C.  South of lat. 30deg.  S. the temperature decreases again rapidly; in the chart no lines are drawn for temperatures below 8deg.  C., as we have not sufficient observations to show the course of these lines properly.  But we know that the temperature at 400 metres sinks to about 0deg.  C. in the Antarctic Ocean.

[Fig. 8]

Fig. 8. —­ Temperatures (Centigrade) at a Depth of 400 Metres (218 Fathoms).