

xxvin.] PETERS' OBSERVATIONS. 411 



and, after having thus oscillated for several times, A adhered at last 

 permanently to B. ... The flashes proceeded with great speed, but 

 not so that the eye might not follow them distinctly. By an 

 estimation of time and known dimension of space traversed, at least 

 an under limit of the velocity may be found ; thus, I compute this 

 velocity to be not less than 200,000,000 metres [or about 120,000 

 miles] in a second. 



" The process described is accomplished in the higher photosphere, 

 and seems not to affect at all the lower or dark atmosphere. With 

 it a second, or rather a third, period in the spot's life has begun, 

 that of dissolution, which lasts sometimes for ten or twenty days, 

 during which time the components are again subdivided, while the 

 other parts of the luminous margin, too, are pressing, diminishing, 

 and finally overcasting the whole, thus ending the ephemeral 

 existence of the spot. 



" Rather a good chance is required for observing the remarkable 

 phenomenon which introduces the covering process, since it is 

 achieved in a few minutes, and it demands, moreover, a perfectly 

 calm atmosphere, in order not to be confounded with a kind of 

 scintillation which is perceived very often in the spots, especially 

 with fatigued eyes. The observer ought to watch for it under 

 otherwise favourable circumstances when a large and ten or twenty- 

 days'-old spot begins to show strong indentations on the margin." 



The scintillation referred toby Dr. Peters is perhaps associated 

 with a phenomenon which has been described by M. Trouvelot, 1 

 who has observed the faculous masses to subdivide into small 

 flakes which vibrate rapidly, producing the effect of a snow- 

 storm above the umbra, when these dissolve into blue or violet 

 vapours. 



It happens sometimes also near groups of spots which are 

 endowed with great activity that perturbations are observed 

 which are so violent that the adjacent photosphere is shaken to 

 its foundations, cracks, and, on opening, forms sinuous crevasses 

 which extend to considerable distances, sometimes connecting 

 the most distant spots with each other. 



1 Bulletin Astronomiquc, vol. ii. 



