IN THE SOLAR SYSTEM:. 



75 



let me say that physicists have estimated that beyond the region of our atmosphere 

 there is no matter as dense as the contents of an exhausted receiver. 



While engaged upon this subject, let us put aside the gross ideas which attach to matter 

 upon the surface of our planet, let us view it as we know it exists in the celestial spaces, 

 and let us be prepared to find in the movements of the ether when impelled by the tre- 

 mendous energies which I shall presently invoke, a rapidity, which knows no parallel 

 among the ponderable agents with which our senses bring us into contact. 



We must now study some of the facts which the observations of eminent astronomers 

 have taught us, concerning the governing orb of our system. 



The sun is known to have an opaque nucleus, surrounded by an atmosphere of vast but 

 unknown height, one stratum of which is luminous, and has received the name of photo- 

 sphere. Certain appearances resembling luminous clouds, seen round the disc of the moon 

 during the time of a total eclipse of the sun, lead to the belief that the sun's atmosphere 

 extends far above the luminous stratum. In that elevated region of the sun's gaseous 

 envelope, there are strong indications of imperfect transparency. 



A close examination of the spots upon the sun's disc, teaches us that it revolves upon 

 an axis, which is inclined to the plane of the ecliptic. 



The determination of the period of the sun's rotation, with the amount and direction 

 of the inclination of its axis, is among the difficult problems of astronomy. Different 

 results have been obtained by different observers. I shall rely upon the accuracy of those 

 furnished by M. Arago for these data, which are of vital importance to the theory I am 

 about to offer. 



According to the authority cited, the sun's axial rotation is accomplished in 25.5 days. 

 The solar equator is inclined to the ecliptic about 7 degrees; and the line of nodes is in 

 longitudes 75° and 255°.* Let me add that the north pole of the sun is incliued toward 

 longitude 345°. 



An interesting feature in the sun's constitution, the study of which has occupied the 

 minds of Henry, Nervander, Carlini, Secchi, and others, is the difference in temperature 

 of different parts of the solar surface. The observations of Secchi have produced more 

 definite results than those of his colaborers in this field of research. 



Secchi made observations upon the sun on the 20th, 21st, and 22d March, 1852, which 

 were unsatisfactory in several particulars. At that time of the year the sun's equator 

 appears at its extreme angular distance from the plane of the ecliptic. The observations 

 were continued only three days, when twenty-seven were requisite for valuable results ; 

 and instead of being made in the line of the sun's axis, the line of a circle of declination 

 was chosen, which on the 21st March lies at an angle of 25° 15' 57" with the former. 



* Astronomie Populairc, vol. ii, pp. 86 and 87. 



