434 



M. Wladimir Michclson on the Distribution 



mum ordinate is progressively displaced toward the more 

 refrangible region. We have indicated above the probable 

 law of this displacement. 



Fig. 3. 



(4) The theoretical curves of the normal spectrum, like 

 Prof. Langley's prismatic curves, are not symmetrical ; the 

 largest area is situated on the right-hand side of the maximum 

 ordinate, that is, on the side of the less refrangible rays. 



(5) In accordance with this, the fall of each curve is more 

 rapid on the side of the shorter undulations. For the two 

 cases of which we have given diagrams, all sensible heat 

 disappears before the curves reach the limit of the visible 

 spectrum : there is only dark heat. 



7. Solar Curve. — I have also endeavoured to compare my 

 theoretical curves, as to general form, with the curve of solar 

 energy beyond the atmosphere. In fig. 4 the separate points 

 correspond to the numbers given by Prof. Langley in No. 9 

 of the table 120 of his work, * Researches on Solar Heat, &oJ 

 The dotted curve has been traced from curve 3 of plate 15 of 

 the same work, and the continuous curve gives the theoretical 

 curve represented by the equation 



L = A*"*\-« 



(17) 



and passing through the observed points A and B. 



To take account of the difference between theory and obser- 

 vation (a greater difference in this case than in the preceding 

 one), we must remember that not only equation (17), but also 



