Eddy.] 'J'^'* [June 10. 



" Radiant Heat an Exception to tlie Second Law of Thermo- 

 dynamics ;" bj H. T. Eddy, Ph.D., University of Cincinnati. 



Pending nominations Nos. 959, 960, 961, and new nominations 

 Nos. 962, 963 were read. 



C. G. Ames was appointed by the President in the place 

 of the late S. W. Roberts as a member of the Committee on 

 the Hall. 



And the meeting was adjourned. 



Radiant Heat an Exception to the Second Law of Thermodynamics. 

 By H. T. Eddy, Ph.D., University of Cincinnati. 



{Read before the American Philosophical Society, June 16, 1882.) 



Since the radiation of heat takes places by propagation through space 

 at a certain finite velocity and not instantaneously, it is quite possible for 

 occurrences to intervene during the exchange of radiations between two 

 bodies such as to essentially change the distribution of heat which would 

 otherwise have ultimately taken place. 



To make this evident, let us employ first a mechanical analogy. In the 

 accompanying figure, let therebe three parallel screens, a, b andc, the latter 

 between the two former and all three perpendicular to the plane of the 

 paper. Let them be pierced respectively by series of equidistant apertures 

 «! 1*2 • • • ^n' i^i &2 • • • Ky C1C2 ■ . . Cq, situated in the plane of the paper, 

 and let these apertures be so placed that a, h^ Cj ai'e upon one straight line, 

 not quite at right angles to the screens ; then are «, b.^ c^, etc., and «„ i„c„ 

 upon lines parallel to a^ b^ c,. Now conceive the screens a b c to have 

 a common uniform velocity u in the direction from the c, to Cy 



Also let a series of projectiles be discharged from any fixed position A 

 at the left of the screen a at such instants as to pass the first one through 

 the aperture a^, the second through a.^, etc., and let the direction of dis- 

 charge be perpendicular to the screens, and the velocitj' v such that 

 each one shall just reach the screen b in time to pass through the first 

 aperture of that screen which crosses its path. Then would the screens 

 a b c m no way interfere with the passage of these projectiles. Let us 

 denote the space at the left of a as the space A, and that at the riglit of b 

 as the space B. Then if there be a continuous discharge of projectiles from 

 all points of the space B, only a part of them can pass through tlie aper- 

 tures of a. Such however as succeed in passing a will pass b and c also. 



Again, let a second discharge of projectiles take place from the space B 

 but directed toward the left perpendicularly to the screens, so that these 

 projectiles move in a precisely opposite direction from those first mention- 



