Ch. XVI.] WHIELAVIXDS AXD CYCLOXES. 303 



TTe thus see that whirlwinds of great violence occur 

 when the air is dry, and there can be no condensation. 

 When, however, they are formed at sea, and occasionally 

 on land, the air next the surface is saturated with mois- 

 ture ; and this moisture is condensed when it is carried 

 to a great height, forming clouds, or falling in showers of 

 rain and hail. This condensation of vapour is an effect, 

 and not a cause, and takes place, not in the centre, but 

 at the top or at the sides of the ascending column. This 

 is well shown in an account, by an eyewitness, of a 

 whirlwind that did great damage near the shore of Lough 

 Neagh in Ireland, in August, 1872.* It was about 

 thirty yards in diameter. It destroyed several hay- 

 stacks, and carried the hay up into the air out of sight. 

 It partially unroofed houses, and tore off the branches of 

 trees. The railway station at Randalstown was much 

 injured ; great numbers of slates, and two and a half 

 hundredweight of lead were torn from the roof. AVhen 

 passing over a portion of the lake, it presented the ap- 

 pearance of a water-spout. On land everything that it 

 lapped up was whirled round and round, and carried up- 

 wards in the centre, whilst dense clouds surrounded the 

 outside and came down near to the earth. 



In Australia I had many opportunities of studying the 

 dust whirlwinds ; and as I looked upon them as the 

 initial form of a cyclone, I paid much attention to them. 

 On a small plain, near to Maryborough, in the province 

 of Victoria, they were of frequent occurrence in the hot 

 season. This plain was about two miles across, and was 

 nearly surrounded by trees. In calm, sultry weather, 



* " Xature," vol. vi. p. 511. 



