ON THE EXTERNAL APPEARANCE OF THE SUN'S 



DISK. 



TRANSLATED FROM THE GERMAN PERIODICAL " AUS DER NATUR," ETC., LEIPZIG, NO. 



11—1864. 



I.\ one of the last meetings of the Astronomical Society of Euglaud, some 

 interesting remarks on the aspect presented by the exterior envelope of the sun 

 were offered by M. Dawes. lie first adverted to the great increase in the num- 

 ber of the observers who apply themselves to the study of that orb. since the 

 number of large telescopes had itself so greatly increased and the dangers inci- 

 dent to the sight been correspondingly diminished. But the appearances in 

 the sun, when carefully studied with these powerful instruments and under 

 favorable atmospherical circumstances, differ so widely from those which had 

 been observed with the imperfect instruments of former times, that it can 

 occasion no surprise if some observers, unapprised of what has been already 

 noticed, should take the objects which fall within the field of their telescope to 

 be new discoveries. That this is sometimes the case, there is every reason to 

 believe. Not this circumstance alone, but still more the new names invented for 

 these supposed discoveries, tend certainly more to impede than to jiromote the 

 advancement of science. It would seem desirable, therefore, that attention 

 should be directed to those appearances which have been long since observed 

 and described, and that they should be collected and compared with the facts 

 which have been more recently verified by the help of the improved telescope. 



To recognize the spotted appearance of the sun, no very great enlargement is 

 necessary. M. Dawes has often observed it with a refractor of only 2^ inches 

 opening, and a magnifying power of 60. If the surface of the sun be observed 

 with an instniment of fromsix to eight inches opening, it presents the appearance 

 of being chiefly composed of luminous masses which are separated from one 

 another by rows of small black points. The interval between these points is but 

 feebly brought out, and is filled with a matter which shines less brightly than 

 the general surface. Whatever the magnifying power employed, the division 

 between the luminous masses seems never to be complete. 



These masses present almost all possible varieties of irregular forms. The 

 rarest of all are those which Nasmyth has compared to willow leaves. They 

 are long, slender, and pointed. This form is only observed in the immediate 

 neighborhood of the larger spots, in their half-shade, and their shadows extend- 

 ing but a small distance from them — a peculiarity mentioned by Dawes as early 

 as 1852, in his description of a new telescope, wherein he also states that the 

 under side of the half-shades appears thickly indented, that lustrous points seem 

 to be directed to the centre of the spots, and that they present, on the whole, the 

 appearance of a band woven of straw whose inner ends have not been brought 

 into close conformity. 



Sir John Herschel has stated, in his Introduction to Astronomy, that the part 

 of the sun's disk which is. free from spots, shines with no uniform lustre ; that 

 the surface of the sun appears dotted with small black points or pores, which, 

 when attentively observed, appear to be undergoing constant change, and that 

 nothing can be more fitly compared with this appearance than the slow subsid- 

 ence of the flakes of a chemical precipitation in a transparent liquid when locjked 

 at from above. M. Dawes has observed and confirms this phenomenon, though 

 U s66 



