Internal Work of the Wind. 437 



Part III. — Application. 



Of these irregular movements of the wind, which take place 

 up, down, and on every side, and are accompanied of necessity 

 by equally complex condensations and expansions, it will be 

 observed that only a small portion, namely, those which occur 

 in a narrow current whose direction is horizontal and sensibly 

 linear, and whose width is only the diameter of the anemo- 

 meter, can be noted by the instruments I have here described, 

 and whose records alone are represented in the diagram. 

 However complex the movement may appear as shown by the 

 diagram, it is then far less so than the reality, and it is prob- 

 able, indeed, that anything like a fairly complete graphical 

 presentation of the case in impossible. 



I think that on considering these striking curves (Plates 

 V., VI., VII., VIII., and IX.), we shall not find it difficult to 

 admit, at least as an abstract conception, that there is no 

 necessary violation of the principle of the conservation of 

 energy implied in the admission that a body wholly immersed 

 in, and moving with such a wind, may derive from it a force 

 which may be utilized in lifting the body, in a way in which 

 a body immersed in the u wind " of our ordinary conception 

 could not be lifted, and if we admit that the body may be 

 lifted, it follows obviously that it may descend under the 

 action of gravity from the elevated position, on a sloping path, 

 to some distance in a direction opposed to that of the wind 

 which lifted it, though it is not obvious what this distance is. 



We may admit all this, because we now see (I repeat) that 

 the apparent violation of law arises from a tacit assumption 

 which we, in common with all others, may have made, that 

 the wind is an approximately homogeneously moving body, 

 because moving as a whole in one direction. It is, on the 

 contrary, always as we see here, filled (even if we consider 

 only movements in some one horizontal plane) with amazingly 

 complex motions, some of which, if not in direct opposition to 

 the main movement, are relatively so, that is are slower, while 

 others are faster than this main movement, so that a portion 

 is always opposed to it. 



From this, then, we may now at least see that it is plainly 

 within the capacity of an intelligence like that suggested by 

 Maxwell, and which Lord Kelvin has called the " Sorting 

 Demon," to pick out from the internal motions those whose 

 direction is opposed to the main current, and to omit those 

 which are not so, and thus, without the expenditure of energy, 

 to construct a force which will act against the main current 

 itself. 



