1 86 



investigated the courses of Atlantic storms. He discussed 

 285 depressions in all, covering an interval of twenty-one 

 months, and found the following percentage proportions : 



Source of Depression. Exist ^| ****' Passing Lpng. 



Arctic regions ....... 8 6 



North America 44 24 



Probably tropical ...... 9 2 



Arising at sea 37 16 



Untraceable ...*... 2 2 



100 50 



You will therefore see that only half of the disturbances 

 which appear in mid- Atlantic live till they reach the Irish 

 coast, and that only one quarter of the storms which visit 

 us ever come from the States or could possibly have been 

 telegraphed from thence. 



The large diagram which I exhibit, and which has been 

 drawn by Dr. Koppen of the Hamburg Meteorological 

 Office, shows the districts of maximum frequency of depres- 

 sions over the Atlantic, on the average of the year. It 

 will be seen from this that a broad belt extends from 

 40 N. over the eastern States and out as far as New- 

 foundland. If the map were extended westwards we 

 should find this belt stretching back to the Rocky Moun- 

 tains. After passing Newfoundland the belt becomes 

 narrower and trends north-eastward, till it touches the 

 permanent Icelandic depression, which exists in the north 

 Atlantic during the greater part of the year. From this 

 point it throws out an arm into Davis's Straits. The main 

 stream, however, passes on, and on the Scandinavian coast 

 forks, one maxima lying near the Loffodens, the other 

 over the southern Baltic. 



