eo 
Fe ee ES ery a ianaaaiinaanagy 
W. T. Sampson—=Spectrum of the Corona. 343 
gneiss are very common in the region. Such facts make it 
evident that the porphyritic structure is a characteristic of 
little relative importance; that a porphyritic variety may have 
rightly a place on a level with other ordinary varieties, but 
never above one based on variations in composition. 
The porphyritic structure is an easy character to observe, 
but this is not an argument in its favor that science can enter- 
tain. Such names as /elsite-porphyre, amygdaloporphyre, granito- 
porphyre, melaphyre (this last signifying “ black porphyry”) and 
others (abbreviated sometimes to felsophyre, amygdalophyre, 
granophyre, etc.) have high authority. But they seem to 
belong rather to books on polished stones than to scientific 
works on lithology. 
[To be continued. ] 
ART. XXXIX.—On the Spectrum of the Corona; by W. T. 
ampson, U.S. N. 
mounted telescope of 34 inch aperture and about five feet focal 
length. In addition I had prepared to use a hand polariscope 
to the sun’s surface or broke off some distance above it. Pre- 
Vious observers were somewhat at variance as to the fact 
