118 PROCEEDINGS OF THE REGENTS. 



Smithsonian Institution, 

 Washington, B. C, March 11, 18G1. 



Dear Sir: In reply to your letter of February 25, requesting that 

 I would give you my views in regard to the currents of the atmos- 

 phere and the possibility of an application of a knowledge of them to 

 aerial navigation, I present you with the following statement, to be 

 used as you may think fit. 



I have never had faith in any of the plans proposed for navigating 

 the atmosphere by artificial propulsion, or for steering a balloon in a 

 direction different from that of the current in which the vehicle is 

 floating. 



The resistance to a current of air offered by several thousand feet of 

 surface, is far too great to be overcome by any motive power at present 

 known which can be applied by machinery of sufficient lightness. 



The only method of aerial navigation which in the present state of 

 knowledge appears to afford any possibility of practical application, is 

 that of sailing with the currents of the atmosphere. The question, 

 therefore, occurs as to whether the aerial currents of the earth are of 

 such a character that they can be rendered subservient to aerial loco- 

 motion. 



In answering this question, I think I hazard little in asserting that 

 the great currents of the atmosphere have been sufficiently studied, to 

 enable us to say with certainty that they follow definite courses, and 

 that they may be rendered subservient to aerial navigation, provided 

 the balloon itself can be so improved as to render it a safe vehicle of 

 locomotion. 



It has been established by observations extending now over two 

 hundred years, that, at the surface of the earth, within the tropics, 

 there is a belt along which the wind constantly blows from an easterly 

 direction ; and, from the combined meteorological observations made 

 in different parts of the world within the last few years, that north 

 of this belt, between the latitudes of 30° and 60°, around the whole 

 earth the resultant wind is from a westerly direction. 



The primary motive power which gives rise to these currents is the 

 constant heating of the air in the equatorial, and the cooling of it in 

 and toward the polar regions; the eastern and western deflections of 

 these currents being due to the rotation of the earth on its axis. 



The easterly current in the equatorial regions is always at the 

 surface, and has long been known as the trade winds, while the cur- 

 rent from the west is constantly flowing in the upper portion of the 

 atmosphere, and only reaches the surface of the earth at intervals 

 generally after the occurrence of a storm. 



Although the wind, even at the surface, over the United States and 

 around the whole earth between the same parallels, appears to be 

 exceedingly fitful; yet when the average movement is accurately re- 

 corded for a number of years, it is found that a large resultant 

 remains of a westerly current. This is well established by the fact 

 that on an average of many years, packet ships sailing from New 

 York to Great Britain occupy nearly double the time in returning 

 that they do in going. 



It has been fully established by continuous observations collected at 



