Lesson in.] THE SUN. 13 



through its transparent atmosphere, where the lu- 

 cid substance is not very intense, or where it is 

 removed by some temporary cause. As some of 

 the spots appear below, and others above the sur- 

 face of the shining fluid, it is reasonable to con- 

 clude that the former are the lower parts of the 

 sun's surface, and the latter his mountains, which 

 project beyond the lucid part of his atmosphere. 

 The former are found to vary in their situation, as 

 they may be hidden or rendered visible by any 

 cause which will accumulate or remove the shining 

 matter : the latter are fixed, with respect to the 

 sun's surface, and are those, by observations on 

 which {lie sun's rotation upon his axis has been 

 determined. From what has been here said, it is 

 hoped you are tolerably well acquainted with the 

 nature of maculae : we will now proceed to the 

 consideration of faculae. 



Faculse, on this hypothesis, are those parts of 

 the solar atmosphere which are brighter, and in 

 general more elevated than the rest. These Dr. 

 Herschel supposes to be " more copious mixtures 

 " of such fluids as decompose each other;'* or they 

 may be called, larger collections of the luminous 

 fluids which form the solar atmosphere, according 

 to the quantity, brightness, and depth of which, the 

 faculce differ in magnitude and intensity. They are 

 more frequently observed near ;he borders, than to- 

 wards the middle of the sun's disc, because, as they 

 are supposed to extend beyond the usual level of his 

 atmosphere those which are near the middle of the 

 disc become edgewise to our view, and are there- 

 fore 



