THE CURRENTS OF THE ATLANTIC. 395 



quently ascends in it ; and, in its ascent, it drags the heated air 

 along with it, and produces an upward current. There is thus an 

 upward rush of heated air and vapour above the heated waters, 

 and an inward rush of cold air from either side to supply its place ; 

 and such a combination of movements will produce a great rotat- 

 ing eddy, much in the same manner as the downward flow of 

 water through a hole in the bottom of a vessel will give rise to a 

 vorticose movement of the whole liquid mass. 



Accordingly, the most terrific hurricanes of which we have any 

 record have been generated on the borders of the Gulf-Stream. 

 In the hurricane of 1780, in the Bermudas, houses were levelled 

 by the gale ; forts were washed away by the waves ; heavy pieces 

 of ordnance were lifted into the air ; and the bodies of animals 

 were carried aloft, and dashed to pieces in the fall. The loss of 

 human life was terrible. It is computed that not fewer than 

 20,000 lives were lost on shore; and on the water no vessel 

 could stand the gale. 



And the Gulf-Stream appears also to exert a marked influence 

 on the course of storms which are engendered in other parts of the 

 Atlantic. Erom the examination of the logs of ships, Captain 

 Maury has ascertained that the gales, which are produced in the 

 Atlantic to the south-east of the current, usually travel to the 

 north-west until they meet it, after which they turn along with 

 it, and follow its course. And, according to Mr. Espy, a similar 

 effect is produced in the case of storms which have their birth- 

 place in the valley of the Mississippi. 



There are two facts which have been brought to light by the 

 Irish meteorological observations, which confirm in a remarkable 

 manner this explanation. The main branch of the Gulf-Stream 

 approaches the coasts of Ireland most nearly at the north-western 

 extremity of the island ; and it is, accordingly, there, if this ac- 

 count be the true one, that the evidences of cyclonic movement 

 .should be most marked. And such is the fact : the track of the 

 centres of most of the cyclones whose course has been investigated 

 lies to the north-west of the island. And in exact accordance with 

 this fact is another of a different kind. I have said that, in the 

 area covered by a cyclone at any moment, the minimum of baro- 

 metric prcaaure is at the centre of the vortex. Hence the frequent 

 passage of cyclones in any particular direction must affect the 

 mean distribution of atmospheric pressure, the prepsuro being most 



