JOURNAL OF PROCEEDINGS. 171 



for the prudent expenditure of the income of the Smithson bequest, and, inasmuch as 

 the proposed experiment is one which, in the minds of the majority of considerate 

 and reflective persons, is of great hazard, the Kegents do not think, whatever might 

 be their individual desire to advance the art of serial navigation, that they would be 

 justified in making an appropriation from the Smithsonian income to assist in this 

 enterprise. 



Any questions which may be propounded to me in regard to the experiment of Mr. 

 Lowe will be cheerfully answered, as far as we have the means of giving the required 

 information. 



I have the honor to be, very respectfully, your obedient servant, 



JOSEPH HENRY, 

 Secretary Smithsonian Institution. 



To Messrs. Jko. 0. Cresson, Isaac Lea, and others, 



Philadelphia. 



Smithsonian Institution, 

 Washington, D. C, March 11, 1861. 



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 atmosphere and the possibility of an 

 application of a knowledge of them to atrial navigation, I present you with the fol- 

 lowing 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 bv 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 serial 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 

 serial locomotion. 



In answering this question, I think I hazard little in asserting that the great cur- 

 rents of the atmosphere have been sufficiently studied to enable us to say with cer- 

 tainty that they follow definite courses, and that they may be rendered subservient to 

 serial 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 meteoro- 

 logical 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 heat- 

 ing 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 current 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 recorded 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 this institution 

 for ten years, from every part of the United States, that, as a general rule, all the 

 meteorological phenomena advance from west to east, and that the higher clouds 

 always move eastwardly. We are therefore, from abundant observation, as well as 

 from theoretical considerations, enabled to state with confidence that on a given clay, 

 whatever may be the direction of the wind at the surface of the earth, a balloon ele- 

 vated sufficiently high, would be carried easterly by the prevailing current in the 

 upper or rather middle region of the atmosphere. 



