448 Admiral Fitz-Roy [March 28, 



would be information just fresh received hy telegraphy of a cyclone 

 actually in progress at a great distance, and working its way towards 

 the locality. There is no doubt that the progress of a cyclone may 

 be telegraphed, and might secure many a ship from danger by fore- 

 warning." 



Successive, or rather, consecutive gyrations, circuits, or cyclones 

 often affect one another, acting as temporary mutual checks, until a 

 combination and joint action occurs ; their union causing even greater 

 effects : as may be seen even in water currents, — as well as in the 

 atmosphere. 



Between the tropics and the polar regions, or in temperate zones, 

 the main currents are incessantly active, while more or less antagonistic, 

 from the causes above mentioned ; besides which, wherever considerable 

 changes of temperature, development of electricity, heavy rain, or 

 these in combination, cause temporary disturbance of atmospheric 

 equilibrium (or a much altered tension of air) these grand agents of 

 nature, the two great currents, speedily move by the least resisting lines^ 

 to restore equilibrium, or fill the comparative void. One current 

 arrives, probably, or acts sooner than the other, — but invariably 

 collision occurs, of some kind or degree, usually occasioning a 

 circuit, a cyclonic or ellipsonic gyration ; however little noticed when 

 gentle, or moderate in force. 



As there must be resistance to moving air (or conflicting currents), 

 to cause gyration, and as there are no such causes, on a large scale, 

 near the equator, there are no storms (except local squalls) in very 

 low latitudes. 



It is at some distance, from about five to twenty degrees, from the 

 equator that hurricanes are occasionally felt in their violence. 



They originate in or near those hot and densely-clouded spaces, 

 sometimes spoken of as the " cloud-ring ^^' where aggregated aqueous 

 vapour is at times condensed into heavy rain (partly with vivid electrical 

 action) and a comparative vacuum is suddenly caused, towards which 

 air rushes from all sides. That which arrives from a higher latitude 

 has a westwardly, that from a lower an eastwardly tendency, due to the 

 earth's rotation, and to the change of latitude, whence a chief cause of 

 the cyclone's invariable rotation in one direction, as above explained. 



The hurricane or cyclone is impelled to the west^ in low latitudes, 

 because the tendency of both currents there is to the westward, along 

 the surface : although one, the tropical, is much less so, and becomes 

 actually easterly near the tropic, after which its equatorial centrifugal 

 force is more and more evident, while the westwardly tendency of the 

 polar current diminishes ; and therefore, at that latitude, hurricane 

 cyclones cease to move westward (re-curve), go then eastwardly, and 

 toward the polar quarter. 



Great and important changes of weather and wind are preceded, as 

 well as accompanied, by notable alterations in the state of the atmo- 

 sphere. Such changes, being indicated at some places sooner than at 

 others around the I3ritish Islands, give frequent premonitions ; and 



