NA TURE 



[May 4, 1905 



in some of them spots appear at a later stage. No of the limb are secured, an opportunity is afforded 

 spot has been photographed unaccompanied by a of studying the changes in the form of large promin- 

 flocculus; in fact, the duration of a spot is only a ences after intervals '^of a few hours. Two examples 

 brief interval in the life-history of a flocculus. of such changes are here illustrated and briefly de- 



Another interesting subject of inquiry is the position 

 of a spot in relation to the flocculus. Spots more 

 generally make their appearance near the head of, 

 or, in other words, precede the apparently trailing 

 masses of the calcium clouds with respect to the solaV 

 rotation, which is from east to west. Some examples 

 of_ these are given in Fig. 4. When there are two 

 fairly large spots in one flocculus, the larger one 

 nearly always precedes the smaller one. 



The composite pictures (Fig. 3) showing the 



(Lower picture taken last.) 



scribed. In Fig. 5 we have two photographs (only 

 the portions of the limb indicating the particular 

 region of the sun in question are shown) which were 

 taken on July 14, 1904, at iih. 8m. a.m. and I2h. 8m. 

 p.m. respectively. It will be noticed that during this 

 interval of about one hour a startling change has 

 occurred to the largest prominence ; not only has its 

 height been considerably increased, but its form has 

 entirely changed. The material radiating the calcium 

 light seems to have been ejected from the chromo- 

 sphere and then to have apparently met a strong 

 current moving polewards (that is, from left to right in 

 the figure) which has thrown this material in that par- 

 ticular direction. The change of height from about 

 50,000 miles to 60,000 miles in this interval corre- 

 sponds to a velocity of nearly three miles a second. 



Not less interesting is the apparent disappearance 

 of the second large prominence in the figure situated 

 on the left. 



.Another example of a change of form of an enor- 



" limb " and " disc " have also brought to light many 

 interesting points which call for further inquiry. In 

 the first place prominences both near the solar poles 

 and equator give strong images in calcium light. 

 Secondly, prominences, which occur nearer the solar 

 poles than the flocculi, do not appear to disturb 

 the regular mottling on the disc in these hip-h lati- 

 tudes. 



Again, an intense flocculus, when on the limb, is 

 not always accompanied by a large prominence. 



These two last mentioned facts seem to indicate that 1 mous prominence pnotograpnea on |uly iq at 

 tloccuh and prominences are not always interdepen- iih. 45m. a.m. and i,\\. 59m. p.m. respectively is that 

 dent phenomena. shown in Fig. 6. this prominence was situated in 



un continuous hne days, when several photographs | the south-east quadrant. The approximate dimensions 

 NO. 1853, ^'OL. 72I 



^ of a large prominence taken with n four ho 

 ween them. (Lower picture taken last.) 



mous prominence photographed on July 



