428 The Origin of the Great Cyclones. [October, 
curve to the north and east, and travel upon a parabolic 
curve, which oscillates with the sun in declination. This 
curve in summer strikes into the Florida coast, and the 
storm which moves along its path strikes on the Georgia 
and Carolina coasts, as did those of the 18th and 26th of 
last August. Their cyclonic intensity is of course reduced or 
nullified when they spread themselves on the land, as was 
noticed in the latter of the two storms just mentioned. 
In summer this curve does not run further westward than 
Alabama and the Alleghanies, and hence the dry and arid 
season in the north-west, whose plains and prairies are then 
so parched that the cattle have often to be driven hundreds 
of miles to the water-course, and kept there till late in Oc- 
tober. Dové himself admits that the origin of cyclones is 
explained ‘‘if we assume that a portion of the south-east 
trade-wind travels far over the Equator into the northern 
hemisphere.”* This I have assumed and proved. My 
reasons for declining his explanation—viz., that “‘ the pri- 
mary cause of the cyclones is the intrusion of the upper 
current (from the coast of Africa) into the (N.E.) trade-wind 
which lies underneath it ’—are quickly stated. 
This view is based upon the existence of an abnormal 
upper current of air which has ‘‘ ascended over Africa, and 
flows away laterally in the higher strata of the atmosphere 
as an easterly wind,” and has, to use Dové’s words, ‘‘ some 
conneéction with the fal) of dust in the North Atlantic,—an 
occurrence which is frequently observed.”—(P. 186). 
To sustain this he cites the fact, noticed by Piazzi Smyth 
on the Peak of Teneriffe, 10,700 feet above the sea, that this 
dust obscured the sun; and he also cites the remarkable 
occurrence of the erupted ashes of the volcano of Cose- 
guina, in Central America, being ‘‘carried by the upper 
counter trade-wind, not only as far as Kingston, in Jamaica, 
a distance of 800 English miles against the direct (or sur- 
face) trade-wind, but also 700 miles to the westward, where 
they fell on the ship *‘ Conway,’ in the Pacific Ocean. 
From this well-known faét he infers that ‘In the higher 
regions of the atmosphere the air does not always move 
regularly from S.W. to N.E., but that the regularity of this 
movement is interrupted by currents flowing from E. to W.” 
(See ‘‘ Law of Storms,” p. 186). 
It must be allowed that these are very slender and meagre 
inductions of fact to bear the weight of his hypothesis. I 
do not deny that his upper current colliding with the surface 
* Law of Storms, p. 264. 
