XXVm EXPLANATION OF THE PLATES. 



The continuous curve line stands for phenomena in the North, and the broken 

 curve line for phenomena in the South Atlantic. Thus the Gales' Curve shows that 

 in every hundred days, and on the average, in the month of January of different 

 years, there have been observed, in the northern hemisphere, 36 gales (36 per cent.) 

 between the parallels of 50° and 55° ; whereas during the same time and between 

 the same parallels in the southern hemisphere, only 10 gales on the average (10 per 

 cent.) have been reported. 



The fact is here developed that the atmosphere is in a more unstable condition in 

 the North than in the South Atlantic ; that we have more calms, more rains, more 

 fogs, more gales, and more thunder in the northern than in the southern hemisphere, 

 particularly between the equator and the 55th parallel. Beyond that, the influence 

 of Cape Horn becomes manifest. 



Pr,ATE XIV. (§ 839) shows the limits of the unexplored area about the south 

 pole. 



Plate XV. shows by curves the prevalence of winds with northing as compared 

 with winds with southing in them in each of the two hemispheres, north and south. 



Plate XVI. shows the Barometric Curve projected according to actual observa- 

 tions at sea, from the parallel of 78° north to the parallel of 56° south, and carried 

 thence to the poles, by conjecture and in conformity with indications. 



