Progress and Problems of Solar Physics. 129, 



others of gigantic explosive violence, rending portions of 

 a spot in ail directions; spots are frequently "bridged," 

 while others have variously colored umbrae, being- 

 brown, brownish-red and purple. Some groups and 

 single spots are of enormous dimensions; descriptions of 

 some of these giant disturbances which have come under 

 the writer's observation during the past twelve years 

 were described in a paper presented to the Iowa Acad- 

 emy of Sciences about a couple of years ago/'^ 



The finest group which has been seen so far during 

 the present cycle of solar activity was during the month 

 of October, 1903, when a spot group of the very first 

 magnitude Avas observed. This disturbance reached a 

 maximum length of 130,000 miles, a width of 40,000 miles 

 and embraced an area of more than 2,400,000,000 square 

 miles of the solar surface. Remarkable aurorae and 

 other widesi)read electrical and magnetic effects were 

 coincident with the appearance of this group. 



The spectrum of sunspots is rather complicated and 

 of great interest; a general absorption takes place along 

 the whole length of the spectrum. In 1883 Professor 

 Young discovered that the upper portion of this spec- 

 trum was of this character mainly, while the middle part 

 of the spectrum was somewhat different, and in large 

 spots with dark nuclei the region between the lines E 

 and F is not continuous, but made up of countless fine 

 dark lines, with here and there probably bright lines, 

 each line being spindle-shaped, tapering to thin fine 

 marks across the penumbra to the general surface of 

 the sun; but the portion of the spectrum between C and 

 D is much more interesting; many lines become much 

 widened and darkened in this region, while others w^hich 

 are ordinarily faint become very conspicuous; some are 

 reversed and become bright, and again many which are 

 usually strong become weak and almost fade out. My 

 esteemed correspondent. Rev. A. L, Cortie, S. J. Director 

 of the Solar Section of the British Astronomical Asso- 

 ciation, has recently presented a paper on the Spectra of 

 Sunspots in the Region B-D to the Royal Astronomical 

 Society ^^^ in which he reviews a series of observations 

 carried on between the years 1890 and 1901, and has 

 classified his results under the following heads: Widen- 



