364 Mr Lawson on the Trade- Winds of Barbadoes. 



At New Rattray (in the parish of Blairgowrie) I observed an ex- 

 tensive flat, or ancient haugh, with its cliff or bank about 80 feet 

 above the River Eright. 



On the Isla, above Airley Castle, there is haugh land on both 

 sides, about 30 feet above the present level of the river. 



On the River Garry, about 3^ miles north of Blair, there are on 

 the east side two terraces, the one about 30 and the other about 50 

 feet above the river; but whether they are the remains of ancient 

 haughs, or the beaches of a lake, it is difficult to determine. 



Remarks on the Trade Winds and other Currents in the At- 

 mosphere, at Barbadoes ; with an Attempt to Develop the 

 Causes of Hurricanes in the West Indies. By Robert 

 Lawson, Assistant- Surgeon, 47th Regiment. Communi- 

 cated by the Royal Scottish Society of Arts. 



(Continued from page 154 of Volume xxxix. of this Journal.) 



Part II. — The Causes, ^c., of Hurricanes. 



40. There are, at present, two views with regard to the 

 phenomena of hurricanes, which have attracted a good deal 

 of attention. One of these, advocated by Mr Espy, of Phila- 

 delphia, assumes that the aqueous vapour in a given column 

 of the atmosphere becomes condensed, and that the latent 

 heat of the vapour, which is consequently liberated, elevates 

 the temperature of the surrounding particles of air, thereby 

 rendering the whole column specifically lighter than the 

 neighbouring portions of the atmosphere ; and these, accord- 

 ingly, in obedience to the laws of gravity, flow inwards from 

 all points towards its base, while it rapidly ascends. On this 

 supposition, the winds around the base of the ascending 

 column should all flow in the direction of the radii of a circle, 

 in the centre of which the base of the ascending column is 

 placed. Professor Hare, of the University of Pennsylvania, 

 has abopted the opinion of Epsey as to the ascending central 

 column, and the centripetal motion of the surrounding air, 

 but conceives that the upward current may, with more reason, 

 be ascribed to tlie attraction of an electrified stratum of air. 



