158 Intelligence and Miscellaneous Articles. 



no more accurate description than is contained in Sir John Herschel's 

 1 Outlines of Astronomy,' art. 387, where he says, " The part of the 

 sun's disc not occupied by spots is far from uniformly bright. Its 

 ground is finely mottled with an appearance of minute dark dots or 

 pores, which, when attentively watched, are found to be in a constant 

 state of change. There is nothing which represents so faithfully this 

 appearance as the slow subsidence of some flocculent chemical precipi- 

 tates in a transparent fluid, when viewed perpendicularly from above." 

 The only part of this admirable description which I should be at all 

 disposed to modify is that relating to the " constant state of change " 

 in the pores. The plan I have uniformly adopted in the minute 

 scrutiny of the solar surface has been to employ very small perfora- 

 tions in the diaphragm-plate of my solar eyepiece (viz. from 20" to 

 60" in diameter), using the highest magnifiers which circumstances 

 would permit. In this way I have frequently kept the same lumi- 

 nous masses and the intervening pores in view for an hour or two 

 together — and have rarely observed any decided change in either, 

 even when well seen with powers from 400 to above 600. Yet very 

 slight atmospheric tremors suffice to give an appearance of almost 

 perpetual variation ; and unless the view is confined within the nar- 

 row limits of a very small field, the eye is apt to become confused in 

 its judgment of the relative positions of objects so minute and deli- 

 cate. 



A striking exception, however, to this comparative quietude is 

 found in the immediate vicinity of spots which are either rapidly 

 enlarging or closing. It is under these circumstances especially 

 that the luminous masses are found to become more elongated. This 

 is also more remarkably the case when they are preparing for a rush 

 across a chasm, and thus forming those luminous bridges which so 

 often intersect considerable spots. The point from which such a 

 rush is about to be made is often indicated by a greater crowding 

 together towards that place, and a general inclination of the longer 

 axis of each of the elongated masses in that direction ; which might, 

 I imagine, be well exemplified by such chemical precipitates as Sir 

 John Herschel alludes to, if they were about to flow through a nar- 

 row spout or opening in the vessel containing them. I have had my 

 attention thus specially directed to such a point at the edge of a 

 spot, and, having placed it in a very small field of view, have watched 

 with great interest the formation of the first portion of the bridge. 

 In this process the luminous masses have the appearance of bits of 

 -straw, all lying nearly in the same direction, though sometimes 

 rather obliquely to the line of the bridge — the sides of the bridge 

 having a jagged appearance, arising from the unequal length of the 

 pieces which compose it. It is a remarkable fact that these bridges 

 are always formed by the bright streaks of the outer stratum, such as 

 are seen projected on the penumbra, without any admixture of the 

 less luminous second or penumbral stratum. Such, at least, is the 

 conclusion I have arrived at after frequent and very careful scrutiny. 

 And so intense is the light of such a line, however narrow, that when 



