76 



THOUGHTS ON" THE INFLUENCE OF ETHER 



Secchi was more happy in the choice of a time for observing the sun's temperature in 

 the year 1855.* The 8th of June was fixed upon, as the sun is then near that part of the 

 heavens where the plane of its equator intersects the ecliptic. 



The latter observations were undertaken with the view of determining the effect of the 

 sun's atmosphere in diminishing the power of its rays. They produced no new facts in 

 the matter of the relative temperature of different parts of the solar surface. 



From an analysis of Secchi's observations on the sun in 1852, M. Arago presents the 

 following summary: Different points of the sun's surface have different temperatures. The 

 rays from the centre of the disc produce most heat, and from that point the heat diminishes 

 towards the margin. At equal distances from the centre of the disc, the polar regions 

 have a lower temperature than those about the equator; and the two hemispheres sepa- 

 rated by the equator have unequal temperatures. The spots produce a diminished tempe- 

 rature, but the faculac do not cause a sensible increase of heat.f 



From Secchi's observations in 1852, Prof. Littrow concludes that the intensity of radia- 

 tion of heat of different points in the sun's disc is different, not only in consequence of 

 the absorption by the sun's atmosphere, but also because every part of the sun's surface 

 really has its peculiar temperature. On the 20th, 21st, and 22d March, the greatest 

 intensity was found 3' north of the sun's centre. The sun's equator was at the time 2.6' 

 north of the centre. The northern and southern hemispheres have unequal temperatures, 

 as well as the hemispheres, divided by a heliocentric circle of declination.^ 



Having collated the data relating to the rotation of the sun, the position of its axis, 

 and the heat of its surface ; having also drawn such conclusions regarding the density and 

 other properties of the ether as observation and analogy have appeared to sanction, let us 

 endeavor to determine what conditions are induced by the sun in the great ethereal ocean 

 of which it is the centre. 



A ponderable elastic fluid of imperfect transparency, resting upon the surface of an 

 incandescent sphere, could not by any possibility remain in a state of rest. 



If the sphere were at rest, and its whole surface of a uniform temperature, there should 

 be upon every part of it alternate ascending and descending currents of the elastic me- 

 dium; but, if any zone were permanently of a higher temperature than the rest of the 

 surfiice, then ascending currents should be permanently established upon such part of the 

 sphere, and descending currents upon those portions where the temperature was of a lower 

 grade. 



We have learned that the parts of the sun's surface which have the highest tempera- 

 ture, are the equatorial regions, and that those having the lowest are the polar regions ; 



* Astronomisohe Nachriohten, No. 1230. 

 I Wunder des Himmels, appendix, p. 818. 



"f" Astronotnie Populaire, vol. ii, p. 173. 



