Proximate Causes of certain WtTids and Sforins. 26.1 



2. The objection just stated to the doctrhies of Mr. Leslie, as ad- 

 vanced in his illustrations of the Huttonian theory of rain, applies 

 with great force here. The source of refrigeration is altogether in- 

 adequate to the production of the effect ascribed to it. Dr. Hare 

 remarks that by every fall of snow, twice as much caloric is liberated 

 as would be yielded by an equal weight of red hot powdered glass. 

 But not only is the amount of rain or snow falling during a north-east 

 storm very great, but the weather itself often becomes intensely cold. 

 Let it now be supposed that the north-east current of air continues 

 to move at the rate of thirty miles an hour, and the upper south-west 



\ current at the same rate in the opposite direction for twenty four 

 hours. The average velocity of the wind during these storms never 

 exceeds this estimate of forty four feet per second — probably it never 

 reaches it. (See the different tables of the velocity of the wind.) 

 The result will be simply that of bringing the air overhanging the 

 eastern part of Maine, and that overhanging the south-western part of 

 Georgia into contact with each other over the' state of Maryland. 

 The effect would be gradually produced, but the total amount would 

 be the same throughout the whole length of the Atlantic coast with 

 that arising from an instantaneous application of the under stratum of 

 the air resting upon Maine, to the upper stratum of that resting upon 

 Georgia. But this would be altogether inadequate to the determin- 

 ation of a fall of snow several inches in depth, and of weather at the 

 same time intensely cold. It is also to be remarked that there is 

 often almost a calm when the rain or snow commences. It is only 

 gradually that the wind makes itself felt and rises to a gale.* 



3. There are good reasons for doubling whether there be any 

 considerable transfer of the air from the north-east towards the south- 

 west during the prevalence of a north-east storm. Suppose a source 

 of heat and rarefaction to exist over the gulf of Mexico ; that the air 

 overhanging it ascends ; that the air of Georgia and the Carolinas 

 comes in to supply its place, and the whole line of the Atlantic coast 

 is affected by the drain established in the south-west quarter. We 

 might look for the following results. The wind would be most vio- 

 lent in Georgia, and would continue to prevail there, until the cause 

 of heat and rarefaction was removed from over the Gulf. In the 

 States more remote, the wind would be feeble in proportion as the 



' See Dr. Mitchill's account of the north-east storm of February, 1803, in the 

 Philosophical Magazine, Vol. xiii, p. 27.>. 



