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emitting a crackling sound; its intensity varying with the force of the storm, and as before said, more intense during the gusts.”
These dust-storms or whirlwinds when transferred to the ocean, would become whirlwinds and waterspouts,—being precisely the same phenomena—and a number of cases are recorded where they have been met with on the borders of typhoons, and of ships having performed various manœuvres to get clear of them.
On the subject of typhoons, a late writer asserts that the true theory of commencement or formation of cyclones in the Atlantic is “the intrusion of the S. E. trade-winds into the area of the N. E. trade-winds; and he tells us that this satisfies all the conditions of the cyclone problem, and is, therefore, the true solution of the origin of cyclones.”
I fail, however, to see that by this he accounts in any way for the progressive motion; and therefore see no reason to change my ideas with regard to the presence and influence of magnetism in these gales.
A few remarks on the barometer may be desirable in connection with this subject; and I will endeavour in as brief a manner as possible to explain its utility and action with reference to the subject of typhoons.
The first indications by the barometer of the presence, in its vicinity, of a typhoon is generally its oscillations or restless condition, which, though sometimes very small, not exceeding 01 of an inch, ought never to be disregarded.
A few cases are on record in which the oscillations at the mercury in the tube have reached 02, and of the same time the oscillation of the water barometer was .28 of an inch. These oscillations are caused by the disturbed condition of the atmosphere in front, and in the vicinity of the advancing gale. If the atmospheric fluid in which we live and breathe was visible to the eye, it would be seen on the approach of a Typhoon to move in great waves over the barometer, like the undulations of a troubled sea after a heavy gale of wind; and as the
