Dr. Seebeck on the Heat of the Prismatic Spectrum. 445 



12. On the physiology of the brain. 13. On the physical 

 characters which distinguish man from the anthropomorphous 

 animals. — By Dr. Harlan. 



14. On the formation of dew, with an examination of the 

 different theories which have been offered to account for it. 

 15. On climate. — By Dr. Hays. 



16. On colour as a character in minerals, and on the li- 

 mited degree of importance to which it is entitled. 1 7. On the 

 opmions entertained by the Wernerians respecting the modi- 

 fications of the surface of the earth by fire.— By Mr. Keating. 



18. On a north-west passage. 19. On hybernation. — By 

 Mr. Lea. 



20. On the circulation of the blood. 21. On respiration. 

 —By Dr. Mitchill. 



22. On comets, with a new theory to account for their tails. 

 — By Dr. Patterson. 



23. Introduction to the study of entomology. — By Mr. Say. 



24. On the rocks which enter into the composition of the 

 globe. 25. On the distribution of rocks into formations. — 

 By Dr. Troost. 



LXVI. On the unequal Evolution of Heat in the Prismatic 

 Spectrum. By Dr. T. J. Seebeck. 



[Concluded from p. 343.] 



WHAT influence will a change in the temperature of the 

 air have on these phaenomena? What is the proportion 

 of the differences of the heat in the spectrum in warm and 

 cold days ? It is easily to be supposed that in cold days the 

 heat in the spectrum will be generally found less, as the 

 air more quickly cools the thermometer, as it is warmed by 

 the light, than on a warm day; which difference will be ex- 

 pressed by smaller figures. The proportion of the degrees of 

 heat in the different colours of the spectrum remains however 

 the same, the experiment being made on a cold or warm day, 

 provided all other conditions are the same, — the days being 

 equally clear, the prisms being the same, the positions normal, 

 the distance of the thermometer and the opening in the shut- 

 ter or in the prism being also similar. If then the blue and 

 violet halves, for example, are compared with the red and yel- 

 low, we shall always obtain the same differences. 



From all the observations and experiments here given, it 

 results that the effects are variously altered by the refracting 

 mediums being of different descriptions, and no less by exter- 

 nal influences. 



riius 



