On St07"ms and Meteorological Observations. 361 



''is 



same phenomenon, still more brilliantly and vividly developed, will 

 appear, vi^hen, instead of the lens, we employ a concave glass speculum. 

 In the same manner, if we affix to the prism a plate of punctured 

 lead and allow a solar beam to pass through, we may behold, at a 

 slight distance from the prism, as many spectra as there are punc- 

 tures in the lead. 



Art. XXL — On Storms and Meteorological Observations ; by 

 Prof. Mitchell, Univ. N. C. 



ON THE POSITION OF THE AXIS OP GYRATION IN STORMS. 



In the 40th number of this Journal an attempt was made to show 

 that certain winds, and amongst other storms those of the Atlantic 

 coast are the result of a gyratory movement of the air about an axis 

 parallel to the plane of the horizon. In a paper by Mr. Redfield in 

 the last or 41st number, whilst the correctness of the views just re- 

 ferred to, so far as thunder storms are concerned, is allowed, it is con- 

 tended that in the great tempests that sweep along our sea board, the 

 gyration is about an axis either perpendicular or moderately inclined 

 to the horizon. The author of the first of these communications 

 does not find himself warranted in abandoning the opinions originally 

 advanced by him, and begs leave here to offer the following additional 

 remarks. 



A sound theory of storms must fulfil three conditions. 



1. It must account for the characteristics of the wind which con- 

 stitutes an important part, though by no means the whole of the phe- 

 nomena, its direction, velocity, etc. 



2. It must account for the precipitation of moisture under the form 

 whether of rain, hail, or snow. 



3. The motion ascribed by it to the aerial currents must be such 

 as the causes known to be active upon the earth's surface, have a ten- 

 dency to generate. 



In my own paper, each of these points received particular though 

 perhaps not satisfactory notice, and I should not have ventured to 

 offer it for publication if I had not supposed that the theory contained 

 in it was shown to satisfy the three conditions. Mr. Redfield's at- 

 tention is directed almost exclusively to the course, velocity, and 

 changes of the wind. His theory does not and cannot account for 

 the rain and snow, and that the motion ascribed by it to the air is such 



