CnAi'. II.] INERTION. 39 



Section VII. — Difference in the Action of Counter-Currents 

 in Equatorial and Polar Districts. 



The conflicting action of the forces of vertical 

 and horizontal circulation in the polar districts must 

 tend to form counter- currents analogous to those of 

 the equatorial districts ; but in them those currents 

 will tend to run against the central streams instead 

 of against that which encircles the district. 



Section VIII. — Connecting Cwn'&ats between Equatorial and 

 Polar Districts. 



Referring to Plate VI., it will be seen that the 

 equatorial stream A b c meets a polar stream pouring 

 down upon it from the north in the neighbourhood 

 of c ; so that, in fact, as the stream A b c opposes o R 

 on one side, it also opposes the polar stream e c 

 (Plate VI.) flowing from the opposite direction on the 

 other side. The southward course of the polar 

 stream ec (Plate VI.) is obstructed on the surface 

 of the ocean by the equatorial stream a b c ; but we 

 have seen that, in consequence of the action of the 

 vertical force of cu'culation, the equatorial stream 

 ABC offers no obstruction to the southward course 

 of the polar stream in the lower strata. The lower 

 strata of the polar stream e c (Plate VI.) must there- 

 fore continue their course southwards as an under 

 current ; to some extent joining the lower strata of 

 the stream a b c as it underruns the course of the 

 surface stream or, in the opposite direction, and 



