The interest with which I regarded these miniature storms was due to the assistance that their study was likely to give in the discussion of the cause of all circular movements of the atmosphere, including the dreaded typhoon and cyclone. The chief meteorologists who have discussed this difficult question have approached it from the side of the larger hurricanes. There is a complete gradation from the little dust eddies up through larger whirlwinds and tornadoes to the awful typhoons and cyclones of China and the West Indies; and it has long been my opinion that if meteorologists devoted their attention to the smaller eddies that can be looked at from the outside, and their commencement, continuance, and completion watched and chronicled, they could not fail to obtain a large amount of information to guide them in the study of cyclonic movements of the atmosphere. Unless the smaller whirlwinds are quite distinct from the larger ones in their origin, the theories advanced by meteorologists to account for the latter are certainly untenable. According to the celebrated M. Dove, cyclones owe their origin to the intrusion of the upper counter trade-wind into the lower trade-wind current.* (* "Law of Storms" page 246.) More lately, Professor T.B. Maury has stated that "the origin of cyclones is found in the tendency of the south-east trade-winds to invade the territory of the north-east trades by sweeping over the equator into our hemisphere, the lateral conflict of the currents giving an initial impulse to bodies of air by which they begin to rotate." Cyclones having thus originated, Professor Maury considers that they are continued and intensified by the vapour condensed in their vortex forming a vacuum.* (* "Quarterly Journal of Science" 1872 page 418.) Humboldt had long ago ascribed whirlwinds to the meeting of opposing currents of air.* (* "Aspects of Nature" volume 1 page 17. ) There is this dynamical objection to the theory. The movements of the air in whirlwinds are much more rapid than in any known straight current, such as the trade winds; and it is impossible that two opposing currents should generate between them one of much greater force and rapidity than either. If force A joins with force B, surely force C, the product, must have the power of both A and B. But even if this fundamental objection to the theory could be set aside, the small whirlwinds could not thus arise, as they are most frequent when the air is nearly or quite motionless.