Mr. T. Dobson on the Theory of Cyclones, Waterspouts, fyc. 443 



such as the appearance of fiery meteors, the loss of sight, the 

 deranged action of the needle, &c. 



As long as the integrity of the conducting column is main- 

 tained and the supply of electric fluid continued, the aqueous 

 vapour through which a cyclone passes will be condensed and 

 accumulated. Hence arises the immense fall of water (always 

 fresh) when a waterspout breaks, and the excessive rains that 

 accompany the passage of the central space of a cyclone. When 

 the condensation is sufficiently sudden and intense, hail and even 

 ice may be formed. The fact marked 4 is thus explained. 



A physical mechanism adequate to the formation of the con- 

 ducting cylinder presents itself in the form of an avalanche 

 (fact 5), and in the sudden ejection from a volcanic crater of 

 long pent-up and highly elastic gases (facts 1, 2, 6 and 7). It 

 follows, moreover, that a waterspout, a tornado, or even a cyclone, 

 may be produced by anything which tends to form a vertical 

 column of considerably less density, or of much greater humidity, 

 than the surrounding atmosphere. Hence the well-known fact 

 that storms follow great battles, great bush fires, &c. 



When an earthquake and a cyclone occur nearly together in 

 the neighbourhood of a volcano, the earthquake indicates the 

 activity of the volcanic forces, and the cyclone bears evidence of 

 a sudden ejection of gases from the crater, although no eruption 

 of flame or lava may have taken place or been observed. (Fact 3.) 

 The atmosphere will be most highly charged with electricity, 

 and therefore the tendency to a violent restoration of electrical 

 equilibrium will be most powerful just after the season of greatest 

 heat, during which the processes of evaporation and vegetation 

 have been most active, and therefore the development and accu- 

 mulation of atmospheric electricity most rapid. Accordingly it 

 is found that cyclones generally originate in tropical regions ; 

 that the hurricane season in any locality is the same as the season 

 of greatest heat; and that waterspouts, tornados, and hail- 

 storms occur on very hot days. The terrestrial electric currents 

 flow towards the magnetic west, and must therefore* decline 

 towards the south in passing from Java towards the Mauritius, 

 and towards the north in passing from the Caribbean Isles 

 (Barbadoes, Martinique, &c.) towards Cuba. This explains the 

 directions of the two great cyclone tracts in the South Indian 

 Ocean and in the West Indies, up to the points where they are 

 found to recurve, but the facts enunciated in (8) concerning the 

 direction of a cyclone's track in middle latitudes remain unac- 

 counted for. With this exception, the electro-dynamical theory 

 of cyclones here proposed will account for every important and 

 definite fact connected with the phenomenon, and will likewise 

 embrace the obviously allied phenomena of waterspouts, tornados, 

 hail-storms, &c. 



2G2 



