xxiv EXPLANATION OF THE PLATES. 



vertical lines, months ; and the horizontal lines, per cents., or the number of days in 

 a hundred. 



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 par- 

 allels 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. 



