42 Professor Mitchell on the Trade- Winds. 



Other arguments of less weight might be added to the above, 

 Jbut if these fail of producing conviction, I have no great hope 

 that the others would be regarded as satisfactory, and shall there- 

 fore omit them. These vortices may be supposed to be either 

 stationary or moveable, regular or irregular, few in number, 

 and having their horizontal much greater than their vertical 

 diameter, or numerous, and rolling in rapid succession across 

 the ocean. The points where there is either a remission of the 

 -breeze, or a calm, will of course mark the separation of an in- 

 dividual from that which succeeds ii. 



The theory here advocated requires the prevalence in the 

 latitude of the United States, of a westerly, or rather north west- 

 erly wind, proceeding from the higher regions of the atmosphere. 

 That westerly winds predominate over the easterly in both he- 

 mispheres, between the 30th and 60th parallels, is shown in a 

 preceding page. That the north-west winds of the United States 

 descend from the higher regions of the atmosphere, is proved 

 by President Dwight, with his usual ability, in a passage copied 

 from his travels, into the 8th volume of this Journal, to which 

 the reader is referred. The progress of scientific discovery, 

 and especially the discovery of the immense power of radiation 

 to cool the surface of the earth, has deprived some of his argu- 

 ments of a part of their value, but the weight and force of the 

 greater number remain unimpaired. 



On the Navigation of the Maranon or Amazons. By Lieut. 

 H. Lister Maw, R. N.* In a Letter to Professor Jameson. 



Sir, 

 I HAVE lately seen the short but very interesting account o^ 

 improvements in the navigation of the Mississippi contained in 

 the number of your Journal for June. The picture of that 

 river in the year 1808 is so admirably drawn, and corresponds 

 so much with what is at present the case on the lower part of 

 the Maranon, that it made me feel somewhat uncomfortable 



• Lieut. Maw is author of the interesting work entitled, " Journal of a 

 Passage from the Pacific to the Atlantic, crossing the Andes in the Northern 

 Provinces of Peru, and descending the Maranon or Amazons." 



