The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1867-12-31

| current" which sweeps past Mauritius and
Bourbon, and thence returns towards the
east. In the Chinese Sea there is the north
! equatorial current, which sweeps round the
East Indian Archipelago, and then merges
into the Japanese current. There is also the
current in the Bay of Bengal, flowing through
the region in which, as we have seen, cyclones
are commonly met with. There are other sea-
currents besides these, which yet breed no
| cyclones. But we may notice two peculiari-
| ties in the currents we have named. 1hey all
| flow from equatorial TO temperate regions, and
! secondly, they are all "horse-shOe currents"
J So far as we are aware, there is but one other
I current which presents both these peculiari-
! ties, namely, the great Australian current,
! between New Zealand and the eastern shores
| of Australia. We have not yet met with any
record of cyclones occurring over the Australian
current, but heavy storms are known to prevail
| in that region, and we believe that when these
| storms have been studied as closely as the
storms in better known regions they will be
found to present the true cyclonic character.
Now, il we inquire why an ocean current
| travelling from the equator should be
"stoI breeder, F" we shall find ready answer.
| Such current, carrying the warmth Of inter
| tropical regions to the temperate zones, pro-
duces, in the first place, by the mere difference
of temperature, important atmospheric dis
turbapces. The difference is so great, that
| Franklin suggested the use of the thermome-
q
means of determining the longitude, since the
! position of the Gulf Stream at any given season
| is almost constant.
But the warmth of the stream itself is not the
only cause of atmospheric disturbance. Over
the warm water vapOr is continually rising;
and, as it rises, is continually condensed Cike
the steam from a lOcomotive) by the colder
air round. "An observer on the moon,"
says Captain Maury, "would, on a winters
| day, be able to trace out by the mist in the
air the path of the Gulf Stream through the
| sea-"
But what must happen when vapor Is con-
| densedl We know that to turn water into
vapor is process requiring-that is, using
| up-a large amount of heat; and, conversely,
the return of vapOr to the state Of water sets
| free an equivalent quantity of heat. The
| amount of heat thus set free over the Gulf
Stream is thousands of times greater than that
which would be generated by the whole coal
supply annually raised in Great Britain.
Here, then, we have an efficient cause for the
widest hurricanes. For along the whole of
| the Gulf Stream, from Bemini to the Grand
! Banks, there is a channel of heated-that is,
rarefed air. Into this channel the
| denser atmosphere on both sides is cOntinu-
ally pouring, with greater or less strength, and
| when a storm begins in the Atlantic, it always
makes for this channel, 'and, reaching it, turns
and follows it in its course, sometimes en-
| tirely across the Atlantic" ''The southern
| points OF America and Africa have won for
themselves" says Maury, 'the name of the
stormy capes, but there is not a storm -fend
in the wide ocean can out-tOp that which
RACES along the Atlantic coast of North
America. The China seas and the North
Pacific may vie in the fury of their gales with
this part of the Atlantic, but Cape Horn and
| the Cape of Good Hope cannot equal them,
certainly in frequency, nor, do l believe, in
fury" We read of West Indian storm so
violent that "it forced the Gulf Stream back
to its sources, and piled up the water to a
height of thirty feet in the Gulf of Mexico.
| The ship Ledbury Snow attempted to ride the
storm. When it abated she found herself
high up on the dry land, and discovered that
| she had let go her anchor among the tree
| tops on Elliott's Key"
BY like reasoning we can account for the
! cyclonic storms prevailing in the North Pacific
| Ocean. Nor do the tornadOes which rage in
parts of the United States present any serious
! difficulty. The region along which these
storms travel is the valley OF the great Mis-
sissippi. This river at certain seasons is con-
siderably warmer than the surrounding lands.
From its surface, also, aqueous vapor is con-
tinually being raised. When the surrounding
air is colder, this vapor is presently con-
densed, generating in the change vast amount
| of heat. We have thus a channel of rarefed
air over the Mississippi valley, and this chan
mel becomes storm track like the correspond
| ing channels over the warm ocean-currents.
The extreme violence of land-storms is prOba-
bly, due to the narrowness of the track within
which they are. compelled to travel. For it
has been noticed that the fury of a sea-cyclone
increases as the range of the "whirl" dimin-
| ishes, and Uice versa.
There seems, however, no special reason
why cylOnes should follow the storm q
in one direction rather than in the
| other. We must, to understand this,
recall the fact that under the tOrrid zones
the conditions necessary to the generation Of
storms prevail far more Intensely than in tenn
! perate regions. Thus the probability is far
| greater that cyclones should be generated at
| the tropical than at the temperate end of the
| storm q. Still it is worthy OF notice, that in
| the land-locked North Pacific Ocean true
| typhoons have been known to follow the
| storm-track in a direction contrary to that
commonly noticed
The direction in which a true tornado whirls
| is invariably that we have mentioned. The
| explanation of this popularity would occupy
| more space than we can afford. Those OF our
readers who may wish to understand the
| origin of the law of cycOnic rotation should
| study Hersohel's interesting work on Mete-
| orology.
| The suddenness with which a true tornado
| works destruction was strikingly exemplihed
! in the wreck of the steamship San Francisco.
! She was assailed by an extra tropical tornado
| when about 300 miles from Sandy Hook, on
! December "a, 1853. In few moments she
| was complete wreck. The wide range OF
| tornado's destructiveness is shown by this
! that Colonel Reid examined one along whose
! track no less than 10 ships were wrecked,
| crinplpd or dismas ted.-I empLe Bar.