PLATE XIIT. 



This i)hotosrapli, \Aiiicli represents the hi;;h-level calciniii vapor, should be 

 compared with lii^s. 1 and 2, Plate X. It will he seen that at this level the 

 peniuiihra is almost comijletely covered, while many of the smaller s])ots are 

 hlotted out. There are also distinct evidences of dark tloccnli. due to ai)sorhing 

 vaitors at still hii,'her levels. Th(> ilhistration necessarily fails to indicate the 

 brilliancy of the bris^htest ernptiv(> phenomena, which on the original negatives 

 are easily distinguished from the ordinary tloccnli. 



158 



