The Philosophical magazine; a journal of theoretical, experimental and applied physics . t 178° C, given by Prof. Langley, I have calculated and tracedthe theoretical citrves for this temperature and for 327° C. =G00° abs. (fig. 3). We see that these curves have all thequalities that Prof. Langley attributes to the curves determinedexperimentally by liim ; that is to say :— (1) The radiant energy represented by the ordinates dimi-nishes on both sides, yet extends indefinitely towards theside of the less refrangible rays. (2) When the temperature increases all the ordinates in-crease, but in un
The Philosophical magazine; a journal of theoretical, experimental and applied physics . t 178° C, given by Prof. Langley, I have calculated and tracedthe theoretical citrves for this temperature and for 327° C. =G00° abs. (fig. 3). We see that these curves have all thequalities that Prof. Langley attributes to the curves determinedexperimentally by liim ; that is to say :— (1) The radiant energy represented by the ordinates dimi-nishes on both sides, yet extends indefinitely towards theside of the less refrangible rays. (2) When the temperature increases all the ordinates in-crease, but in unequal proportion. Those which represent theenergy of the more refrangible waves increase always morerapidly than those which correspond to the longer undulations. (3) Hence the fact, independently observed, that the maxi- * Stefan, Sitzber. Wien. Akad. vol. Ixxix. p. 301 (1879). 434 M. Wladimir Michelsoii on the iJistiihution muin ordinate is proorressively (Hs|ilaced toward the moreretr;mtjil)le r(<;i()n. We liave indicatod above the probablehiw of this displacement. Fig. (4) The theoretical curves of the normal spectrum, likeProf. Langleys prismatic curves, are not symmetrical ; thelargest area is situated on the right-hand side of the maximumordinate, that is, on the side of the less refrangible rays. (5) In accordance with this, the fall of each curve is morerapid on the side of the shorter undulations. For the twocases of which we have given diagrams, all sensible beatdisappears bc^fore the curves reach the limit of the visiblespectrum : there is only dark heat. 7. Solar Ctiire.—I have also endeavoured to compare mytheoretical curves, as to general form, with the curve of solarenergy beyond the atmosphere. In fig. 4 the se{)arate pointscorrespond to the numbers given by Prof. Langley in No. 9of the table 120 of his work, Researches on Solar Heat, & dotted curvt^ has been traced from curve 3 of plate 15 ofthe same work, and the continuous curve gives the
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