136 RUMFOED SPECTROHELIOGRAPH. 



spectrolieliograpli is not yet sufficient for extended generalizations, 

 the variety of phenomena recorded is snch as to call for some comment 

 here. A more complete discussion of the results must be reserved 

 for a future occasion. 



ON THE NATURE OF THE (•AliCIITM FLOCCULI. 



In my first published note on the bright calcium regions recorded 

 for the first time Avith the Kenwood spectrolieliograpli T briefly 

 described the results in the folloAving words: 



The reversed regions are of great extent and in appearance closely resemble 

 facnhp. Several explanations may be suggested to account for them. They 

 may he : 



1.. Ordinary prominences projected on the disk. 



2. I'rominences in which H and K are bright, while the hydrogen lines are 

 absent. 



3. Facula?. 



4. Phenomena of a new class, similar to facula', but showing H and K bright, 

 and not ol)tained in eye observations or ordinary photographs because of the 

 brilliant l)ackground upon which they are projected." 



It was sul)se(|uent]y shown that the l)rig]it calcium regions in gen- 

 eral coincide closely with the faculte, and it was concluded that they 

 represent the hot calcium vapor in the upper part of the faculse and 

 in the lower part of the adjoining chromosphere. Fig. 1, plate ni, 

 which is reproduced fi-om a photograph of the K line taken at Ken- 

 wood Observatory, sIioaas that the bright reversals of the K line fre- 

 quently occur in regions of the disk where the continuous spectrum is 

 considerably strengthened. These regions are the factdse proper. 

 The facuLa!, though apjiarently but little brighter than the photo- 

 sphere, are conspicuously visible near the sun's limb. This is prob- 

 ably due to the fact that they reach a higher level, and thus escape 

 much of the general absorption exercised by a comjiaratively thin 

 stratum of a smoke-like nature which lies in close contact with the 

 photosphere. The faculse are, in general, the regions above which 

 the calcium vapor is hottest and most brilliant. 



But it appeared later that the calcium vapor is not confined to the 

 faculae, but extends beyond their boundaries and frequently occurs in 

 regions of the solar disk where they are absent. The generally close 

 coincidence of the calcium clouds with the faculse, and a natural hesi- 

 tation to propose a new name before the results obtained with the 

 spectrolieliograpli had been sufficiently studied, led me to apply this 

 term to the bright calcium regions photographed with the spectro- 

 heliograph. From my present point of view I think it would have 

 tended to clearness, as M. Deslandres has pointed out, if some other 

 name had l)een adopted. 



^Astronomy and Astrophysics, Vol. II (1892), p. 159. 



