1861] WKITINGS OF JOSEPH HENRY. 443 



ON THE UTILIZATION OP ATMOSPHERIC CURRENTS IN AERO- 

 NAUTICS.* 



(From the Smithsonian Annual Report for 1860, pp. 118, 119.) 

 March 11, 1861. 



Dear Sir : In reply to your letter of February 25, 1861, 

 requesting that I would give you my views in regard to the 

 currents of the atmosphere and the possibility of an applica- 

 tion 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 diflferent from that of the 

 current in which the vehicle is floatins:. 



The resistance to a current of air offered by several thou- 

 sand 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 prac- 

 tical application is that of sailing with the currents of 1th e 

 atmosphere. The question therefore occurs as to whether 

 the aerial currents over the earth are of such a character that 

 they can be rendered subservient to aerial locomotion. 



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 ren- 

 dered subservient to aerial navigation provided the balloon 

 itself can be so improved as to render it a safe means of 

 locomotion. 



It has been established by observations now extending 

 over two hundred years, that at the surface of the earth 



* [A letter addressed to Mr. T. S. C. Lowe, the Aeronaut, dated "Wash- 

 ington, D. C., March 11, 1861.] 



