876 SPECIAL RESULTS IN THE URANOLOGICAL 



luously, large openings with their dark centres or nuclei 

 surrounded by penumbras or " shallows." 



The black nuclei of the solar spots, which are seldom 

 round, but, on the contrary, almost always characterised 

 by corners, jagged edges, and re-entering angles, are 

 often surrounded by penumbras in which the same figure 

 is repeated on a larger scale. There is no perceptible gra- 

 dual transition from the colour of the nucleus to that of 

 the penumbra, or from the penumbra, which has some- 

 times a filamentous appearance, to the photosphere. Ca- 

 pocci, and a very diligent observer, Pastorff, (at Buckholz, 

 near Frankfurt on the Oder), have given very exact draw- 

 ings of the angular forms of nuclei, (Schum. Astr. Nadir. 

 No. 115, S. 316, No. 133, S. 291, and No. 144, S. 

 471). William Herschel and Schwabe saw the dark 

 nuclei crossed by shining veins of light, and even by, as it 

 were, "luminous bridges," phenomena of a cloud-like 

 nature belonging to the second stratum which produces 

 the penumbras. These singular forms, probably the conse- 

 quences of ascending currents, the tumultuary formation and 

 appearances of spots, faculae, furrows, and projecting ridges 

 (the crests of luminous waves), are regarded by the astro- 

 nomer of Slough as indicating powerful evolution of light ; 

 while on the other hand he considers the absence of solar spots 

 and their accompanying phenomena to indicate comparative 

 feebleness of combustion, and consequently a less degree of 

 beneficial action on the temperature of our planet and on 

 vegetation. These conjectures led Wm. Herschel to attempt 

 to bring into comparison and connection the absence of solar 

 spots in the years 1676 1684 (according to Flamstead) ; 

 from 1686 to 1688 (according to Dominique Cassini) ; from 



