EXAMINATION OF REID'S STORMS. 207 



in that climate. The condensation of this vapor, as I have 

 demonstrated by experiment, would give out into the air 

 in contact with the condensing vapor, caloric of elasticity 

 sufficient to expand that air between five and six thousand 

 cubic feet for every cubic foot of water generated, after 

 making allowance for the diminished volume due to the 

 condensation of the vapor itself into water. 



This will cause the barometer to fall more than two 

 inches in the centre of the storm, and to rise all round on 

 the outside of the storm, especially on that side towards 

 which the top of the cloud is pressed by the upper current 

 of the atmosphere into which the cloud penetrates ; and 

 that will be the direction in which the storm will move 

 along the surface of the earth ; all which I have elsewhere 

 shown. 



As the cloud moves along, being pushed by the upper 

 current, the air under the cloud will, on account of the 

 specific levity of the cloud, ascend, and thus the action will 

 be continued. Moreover, I have demonstrated from ex- 

 periment that if the barometer falls two inches under the 

 base of one of these clouds, the air will not have to ascend 

 so high, by eight hundred yards, before it begins, by the 

 cold of diminished pressure, to form cloud; and this, in 

 many cases, will bring the cloud down on the surface of 

 the sea ; or in other words the vapor of the air in the out- 

 side of the storm will begin to condense, as soon as it comes 

 under the base of the cloud, from the cold produced by 

 diminished pressure there. 



154. It is not a little remarkable, that all these storms, 

 and others which have been traced in the West Indies, 

 travelled towards the N. W. almost at right angles to the 

 direction of the trade wind in those latitudes ; but very 

 nearly, if not exactly, in the direction of an upper current 

 of the air, known to exist there towards the N. W. The 

 direction of the trade wind will therefore produce an oblique 



