Internal Work of the Wind. 429 



potentiality of what may be called " internal work " * in the 

 wind. 



On farther study, it seemed to him that this internal work 

 might conceivably be so utilized as to furnish a power which 

 should not only keep an inert body from falling, but cause it 

 to rise, and that while this power was the probable cause of the 

 action of the soaring bird, it might be possible through its 

 means to cause any suitably disposed body, animate or in- 

 animate, wholly immersed in the wind and wholly free to 

 move, to advance against the direction of the wind itself. 

 By this it is not meant that the writer then devised means for 

 doing this, but that he then attained the conviction both that 

 such an action involved no contradiction of the laws of motion, 

 and that it was mechanically possible (however difficult it 

 might be to realize the exact mechanism by which this might 

 be accomplished). 



It will be observed that in what has preceded it is intimated 

 that the difficulties in the way of regarding this even in the 

 light of a theoretical possibility may have proceeded, with 

 others as with the writer, not from erroneous reasoning, but 

 from an error, in the premisses, entering insidiously in the 

 form of the tacit assumption made by nearly all writers, that 

 the word " wind " means something so simple, so readily intel- 

 ligible, and so commonly understood, as to require no special 

 definition ; while, nevertheless, the observations which are 

 presently to be given show that it is, on the contrary, to be 

 considered as a generic name for a series of infinitely complex 

 and little-known phenomena. 



Without determining here whether any mechanism can be 

 actually devised which shall draw from the wind the power 

 to cause a body wholly immersed in it to go against the wind, 

 the reader's consideration is now first invited to the evidence 

 that there is no contradiction to the known laws of motion, 

 and at any rate no theoretical impossibility in the conception 

 of such a mechanism, if it is admitted that the wind is not 

 what it has been ordinarily taken to be, but what the following- 

 observations show that it is. 



What immediately follows is an account of evidence of the 

 complex nature of the " wind," of its internal movements, of 



* Since the term " internal work " is often used in thermodynamics to 

 signify molecular action, it may be well to observe that it here refers not 

 to molecular movements, but to pulsations of sensible magnitude, always 

 existing in the wind, as will be shown later, and whose extent and extra- 

 ordinary possible mechanical importance it is the object of this research 

 to illustrate. The term is so significant of the author's meaning, that he 

 permits himself the use of it here, in spite of the possible ambiguity. 



