ie 
254 
First. I found that the view to which the hypothesis directly 
leads, that the metallic prominences are produced by violent 
explosions due to sudden expansions among the cooler matters 
brought down to form the spots, when they reach the higher 
temperature at and below the photo -vel, includes all the 
facts I know touching spot and prominence formation. 
for instance, the close connection between metallic prominences 
and spots ; the entire absence of metallic prominences with rapid 
motion from any but the spot-zones; the fact that the facule 
always follow the formation of a spot and never precede it ; 
here | 
hus, 
NATORE 
[Fuly 15, 1886 
that the faculous matter lags behind the spot asa rule ; the exist- 
ence of veiled spots and minor prominences in regions outside the 
spot-zones ; the general injection of unknown substances into the 
lower levels of the chromosphere which I first observed in 1871, 
and which have been regularly recorded by the Italian observers 
since that time—all these phenomena and many others which 
may be referred to at length on another occasion, are demanded 
by the hypothesis, and are simply and sufficiently explained 
by it. 
With regard to the extensions of volume to which I have re- 
Most Widened. Lines... F-b Region. 
1879-80" 1880-1 18Bl-2 1682-3 1883-4 1884-5 
fexsfo) 
“Hundred: ont Hundied 3%! Hundred 4t* Hundred st*Hundred: 6th Hundred 7hHundred 
Fic. 1.—Number of appearances of known and unknown lines. 
ferred, I find that if we assume that metallic iron can exist in 
any part of the sun’s atmosphere, and that it falls to the photo- 
sphere to produce a spot, the vapour produced by the fall of 
1,000,009 tons will give us the followinz volumes :— 
Volume in 
Temperature Pressure phic miles 
2,005° C, 380 mm. awe 0°35 
10,000 760! as 1'8 
20,0°0 5 atmos, a0 O'7 
50,000 760 mm. oan $8 
50,009 190 shies 
If we assum? the molecule of iron to be dissociated ten times 
by successive halving, then the volume occupied will be 1024 
times greater, and we shall have 
Volume in 
cubic miles 
9,011 
36,044 
In these higher figures we certainly do seem nearer the scale 
on which we know solar phenomena to take place ; the tremen- 
dous rending of the photosphere, upward velocities of 250 miles 
a second, and even higher horizontal velocities according to 
‘Temperat ire Pressure 
760 mm. 
190 ,, 
50,000° C. 505 
50,000 
