TRANSACTIONS OF THE SECTIONS. 38 



perihelion distances less than '5, that the perihelia of comets with very small peri- 

 helion distances exhibit no greater tendency to crowd about the solar apex than 

 comets with larger perihelion distances. 



On Solar Spots observed during the past Eleven Years, 

 By the Rev. Fkedeeick Howlett, F.R.A.S. 

 The paper was illiisti-ated by numerous veiy carefully executed drawings, enlarged 

 from others which had been micrometrically observed and drawn at the telescope, 

 chiefly by means of projecting the sim's image on a screen. It was well known 

 how lich the years 1859 and 1860 were in solar spots ; and the eleven-year period 

 was again being sti'ikingly corroborated by the nimiber and size of the groups and 

 individual spots of the present year, and which may be expected to prevail until 

 1871. Magnificent groups which appeared in the sun's northern hemisphere in 

 March, April, and August, in almost precisely the same heliographic latitude and 

 longitude, would apparently seem to evince that the disturbing causes, whatever 

 they were, had localized themselves on the disk — not, however, without long 

 inteivals of comparative repose. The forms assimied by the faculte were described 

 by the author, who felt convinced that they were attached, for the time being, to 

 the photosphere, and that they were not clouds floating above it ; otherwise they 

 would frequently impinge on the penumbrse in ways very different from those in 

 which, in point of fact, they are seen to occur. If they consist of simply photo- 

 spheric matter, however, it would seem to be in some compressed or other^vise 

 peculiar manner ; inasmuch as the coarser mottling, so plainly to be distingaiished 

 on all other parts of the sun's suiface, can never be detected on the faculse, and 

 especially on those masses enclosed more or less at times within the receding mar- 

 gins of the penumbra}. Dr. Huggins, however, has detected the finer or rice-grain 

 specks of light in some of the more diffused forms of the faculse. There is appa- 

 rently no dii-ect relationship between the amount of solar-spot disturbance and the 

 terrestrial magnetic storms. The author, however, has suggested the possibility of 

 there being some degree of coiTelation between groups of a peculiarly cyclonic 

 arrangement and unusual magnetic disturbances ; none, or next to none, of the spots 

 had been found to possess any tendency to rotate as it were on an axis — as has, 

 however, been occasionally witnessed by other observers. An instance was given 

 (illustrated by a drawing) how a diff"used penumbral speck was observed to draw 

 ill towards the neighbouring umbra of a solar spot at the rate of 12 seconds of arc 

 in four hom's, which is equivalent to about 660 yards per second (and closely 

 similar to observations of the same kind by Chacornac). As the speck drew in 

 towards the umbra it assumed a continually more narrow and wedge-shaped form 

 (the apex towards the du-ection of advance), and which, therefore, might well be 

 taken to indicate that down-rush into the umbra aforesaid insisted upon by Mr. 

 Norman Lockyer. Assuming, as the author does, that the spots are depressions in 

 the solar photosphere, filled up by the solar gaseous atmosphere, this is evinced, 1st, 

 by the oi-dinary testimony of the eye ; 2udly, by the stereoscopic effect obtained by 

 Mr. De La Rue's photogi-aphs of spots taken at intervals of about two days ; 3rdly, 

 by the foreshortening of the penumbra of a neat circvdar spot, alternately on the right 

 and left side, as it first comes on, and then passes off" the disk — a phenomenon first 

 noticed by Dr. Wilson in the last century ; and 4thly, by the elegant spectro-baro- 

 metric e\'idence (as the author termed it), whereby the progressive thickening of 

 the dark solar absorption-lines, as they pass successively over the spectrum of the 

 photosphere, penumbra, and imibra, seemed to prove an increasing density and 

 depth of an absorbing solar atmosphere. It is, however, urged by Kirchhoff", Donati, 

 and some others (and in a measm-e admitted by Browning) that like effects simi- 

 lar to those four above enimierated might be produced were the spots cloudy 

 condensations, and not depressions. The author called attention to a delicate way 

 (not readily to be noticed without projecting the sun's image on a screen) in which 

 a fine trailing serpentine arrangement of minute specks of penumbral matter may 

 be sometimes seen either following in the wake of a large spot, or meandering 

 amidst a group of spots, indicating the resolution of two or more forces, partly, 

 perhaps, cyclonic, and partly centrifugal, as connected with the sun's axial rotation. 



