HUTCHISON'S OBJECTIONS, WITH REPLIES. 459 



paratively cold land surface, clouds should rapidly begin to 

 form and increase in density till rain begins to fall? The 

 surface of the land being then so much colder than the in- 

 cumbent atmosphere brought by a southerly wind from the 

 Mediterranean, cannot give rise to an upward vortex upon 

 any principle that I can conceive; but, on the contrary, by 

 communicating its coldness to the incumbent atmosphere, 

 and thereby increasing its specific gravity, should rather 

 counteract any tendency to an upward vortex of air. 1 In 

 like manner, in the United States of America, where you 

 reside, when the wind, during the depth of winter, blows 

 from an easterly direction, that is, from the Atlantic, and a 

 then warmer climate, clouds begin rapidly to form and rain 

 follows, in consequence of the reduction of temperature 

 which the comparatively warm atmosphere from the At- 

 lantic undergoes in being transported over the then cold 



1 The effect here, I think, is put for the cause, and if so, the whole difficulty 

 vanishes. The blowing of the south wind at Marseilles is not the cause of 

 the formation of cloud, but the formation of cloud and the commencement 

 of the south wind are simultaneous effects of the same cause. Now this 

 south wind will bring with it a high dew point, and, of course, a light air, 

 well calculated to run in under the base of a cloud already formed, and from 

 the high steam power which it contains, calculated to increase its power of 

 upward motion. 



It is asserted that clouds begin to form after the south wind begins to blow : 

 but if it should be discovered hereafter that the clouds begin to form at the same 

 time, the whole phenomenon is explained, and another strong link is added to 

 the chain of evidence which is already formed in favor of the law of storms for 

 which I contend. Now I have known many instances of long continued rains 

 in the north, while there was a constant south wind, or rather west of south, in 

 consequence of oblique forces operating generally to produce that effect in this 

 latitude; and I never yet heard of a great rain in the western part of. New 

 York, without a southern wind at Philadelphia. And it will be very readily 

 seen, that any air, however cold, if it is near the borders of a lofty cloud, will 

 run in under that cloud, and be forced to ascend, when it comes under it, if a 

 cloud has indeed the specific gravity which I assign to it : so that although 

 a warm south wind blowing over a cold surface of land may be unsuited to 

 originate an upward motion of air, yet it is well calculated to continue that 

 upward motion after it is originated. 



