16 Northers of the Mexican Seas. 
seas.* Perhaps the tardy progression in this case was owing to- 
the proximity of the storm to the equatorial region and to a slug- — 
gish state of the aerial currents then prevailing on its track. 
These five storms may be viewed as belonging to one group ; 
in the great system of storm paths; a system which appears to me 
as resulting directly from the dynamical ence of the diurnal — 
and orbital revolutions of our planet. 
Gales distinguished as Northers, in the Seas of nies and 
Central America. 
The term Northers may well be applied todet to such storms — 
as the first four comprised in the above table, which passed west- 
wardly through the Mexican sea; for their vorticular rotation be-- 
ing in the direction from right to ‘left, thus, ©), they necessarily, © 
on arriving near the coast, commenced to blow from some north-~ 
ern point of the horizon. 
- But the term is most frequently and technically applied to the 
numerous gales which visit the seas of Mexico and Central Amer- — 
ica from September to April, and which are almost unknown ~ 
among the islands of the Antilles or West Indies. 'T'wo of these — 
Northers, of much interest, will next claim our attention. 
* Mr. Tom computes the diurnal orem of the Rodriguez hurricane of April, 1843, — 
in the South Indian Ocean, at about r 230 miles, or between nine and ten miles an 
hour, during its early stages in the salibe vatbars and that it gradually diminished 
when near the tropic, it scarcely exceeded fifty wiles per day. 
‘Mr. Tom appears to think that the hurricanes of that region Sate, <r up and ; 
near the southern margi 
e southeast 4 cannot 
reconcile with previous observations in the two hemisphe wider oat of obser- — 
vation than was had in the Rodriguez storm would seey Aas that Kaas hurricanes — 
turn eastward in their course, after crossing the tropic, and that they are identical with 
some of the violent aes which —_ ships fall in with while running eastward in the - 
of south lati 
Southern Ocean, betw 
The Rodriguez deceens may commenced its sete erly course soon after crossing — 
and its slow rate in “ ke I ascribe, chiefly, if not wholly, to the gradual — : 
the tropic ; 
cessation of its westerly progre 
I apprehend that toa like Seg in the winds from a westerly to an easterly progres 
sion, and vice versa, is also to be ascribed, mainly, the several parallel belts of calms and 
_ variables which are found on the exterior borders of the trade sary: between the trades 
and the 
soon winds, and on the equator. Such a system of changes in the great 
winds of the globe, in the regions referred to, I deem may be fully established by a proper — 
analysis of existing authorities and observations. 
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