1852,] On Dust Whirlwinds and Cyclones. 143 



gradually declines from the equator to the poles — on the equator 

 alone, it will be equable ; but on the either side of it, North and South, 

 the force of rotation will constantly diminish towards the poles. 



Matter floating in the atmosphere will doubtless be influenced by 

 this rotation of the earth, and have communicated to it, a tendency to 

 deviate from a direct parallel line with the equator : — 



The line so formed will, if traced, form an ascending or descending 

 spiral towards the North and South poles, as described in the dotted 

 lines of Plate 4. 



For the Northern Hemisphere this line will form an upward spiral 

 from right to left — or against the hands of a watch — and in the South- 

 ern Hemisphere, the spiral will move in a contrary way, viz. from left 

 to right or with the hands of a watch — coinciding with the known 

 evolutions of these storms on either side of the equator. 



This then may exhibit something of the element we require in 

 order to give these Cyclones their respective rotatory motions. 



But their impetus, and direction when in contact with the earth's 

 surface, will perhaps depend on other causes, the operation of which, 

 though slight, may be sufficient to determine the size of their revolu- 

 tions and the direction of their track — Plate 4 is intended to illustrate 

 this idea. 



The arrow represents the Equator, and the earth's diurnal rotation, 

 from west to east. The dotted lines, mark the tendency of bodies 

 floating in the atmosphere to be drawn towards the poles. 



The spirals are Cyclones ; and the curved arrows with dotted lines, 

 the element that gives them tendency to revolve either to right or left. 

 Additional Notes. 



More extended observations on dust whirlwinds and other meteoro- 

 logical phenomena, confirm me in the belief that all kinds of storms, 

 especially those of a distinct rotatory character, are occasioned by 

 electrical Spirals, of which mention was made in my former paper. 



What the exact nature of those spirals is, I cannot say — possibly 

 some modification of matter not yet fully noticed ; and they may be 

 identical with the electro-magnetic cylindrical-beams supposed by 

 the late Dr. Dalton to compose the Aurora. — Vide Note 2. 



As they are transparent, their existence can only be inferred by the 

 effect produced .on surrounding matter, as in the case of the water 



