On the Theory of the Evening Glow and analogous Phenomena. 275 



Assuming all the proteine compounds ingested in these cases 

 to be assimilated, and transformed without waste into an equal 

 weight of muscle, 1 grm. of muscle, giving by its disintegration 

 1848 metrekilogs. of force (Frankland, Phil. Mag. vol. xxxii. 

 p. 188), the muscle so formed would in each case give — 



A. B. 



Metrekilogs. Metrekilogs. 



146,842 143,335 



the latter quantity being less by 16,677 metrekilogs. than the 

 daily expenditure in the work of the circulation and respiration, 

 given by Helmholtzand Fick at 160,012 metrekilogs (Idem). 



It might be objected that the prisoners live in a higher tem- 

 perature than the subjects observation on whose circulation and 

 respiration furnished the above data ; but the quantity of clothing 

 worn is so small, and loss of heat by evaporation and radiation con- 

 sequently is so much greater in the one case than it was (probably) 

 in the other, that the effect of this difference of temperature is 

 probably neutralized at least by these attendant conditions. But 

 if it be admitted that the difference of 10 per cent, can be so 

 accounted for, the source of external work must be looked for 

 elsewhere than in the disintegration of muscular tissue, as in this 

 case the whole of the muscle formed from the food would be 

 required to furnish the internal work alone. The proportions of 

 proteine compounds given in the Table are above the truth, in 

 many cases considerably so ; and the result is, the energy ob- 

 tained must be considered an exaggeration. 



Madras. 



XXXVI. Theory of the Evening Glow and analogous Phenomena. 

 By Dr. E. Lommel*. 



IN the following pages a theory of the evening glow and of 

 analogous phenomena, based on the principle of the dif- 

 fraction of light, is developed in an elementary form, the fun- 

 damental idea of which I have already stated and treated analy- 

 tically on a former occasion f. I venture now to reproduce the 

 theory in a new and what seems to me a more perfect form, and 

 at the same time to discuss an objection which has been raised 

 against it. 



1. If a pencil of parallel luminous rays from a very distant 

 luminous point meets a dark screen provided with a circular aper- 

 ture, the elementary rays which each point of the aperture sends 



* Translated from Poggendorff's Annalen, vol.cxxxi.p. 105 (June 1867). 

 t " Contributions to the Theory of the Diffraction of Light," Grunert's 

 Archiv, part xxxvi. 1861. 



