Intelligence and Miscellaneous Articles. 461 
ring-clamps to the tail-piece of the 23-inch equatoreal of the 
Halsted observatory, so that the image of the sun falls directly 
upon the slit. 
The detailed examination of the spot-spectra has been thus far 
confined mainly to a few limited regions in the neighbourhood of 
C, D, and b. 
"With the high dispersive power employed, the widening and 
"winging" of the heavier lines of the spectrum is not well seen, 
not nearly so well as with a single-prism spectroscope. All diffuse 
shadings disappear much in the same way as the naked-eye markings 
on the moon's face vanish in a powerful telescope — to be replaced 
by others more minute but not less interesting. In a few spots, 
however, the broadening of the D's and the reversal and occasional 
" lumping " of C has been noticeable even with this high dispersion. 
But the most striking result is that, in certain regions the spectrum 
of the spot-nucleus, instead of appearing as a mere continuous 
shade, crossed here and there by markings dark and light, is resolved 
into a countless number of lines, exceedingly fine and closely packed, 
interrupted frequently between E and E (and occasionally below E) 
by lines as bright as the spectrum outside the spot. These bright 
lines, so far as the eye can determine, may be either real lines 
superposed, or merely vacancies left in the shading of fine dark lines, 
since they are not sensibly brighter than the ordinary background 
of the surrounding spectrum. 
The darker and more intense the spot, the more distinctly the 
fine lines come out, both the bright and the dark ; and so far as I 
have been able to make out yet, there is no difference as regards 
these fine lines between one spot and another. I have never yet 
seen any evidence of displacement in them due to motion, no 
" lumpiness " nor want of smoothness in them. 
"When seeing is at the best, and everything favourable, close 
attention enables one to trace nearly all these lines out beyond the 
spot and its penumbra. But they are so exceedingly faint on the 
sun's general surface that usually they cannot be detected outside 
the spot-spectrum. This resolution of the spot-spectrum into a 
congeries of fine fines is most easily made out in the green and blue. 
Near D, and below it, it is much more difficult to see ; and I am not 
even quite sure that this structure still exists in the regions around 
C and below it. Here, in the red, even with the highest dispersion 
and under the most favourable circumstances of vision, the spot- 
spectrum appears simply as a continuous shade, crossed here and 
there by widened and darkened lines, which, however, are very few 
and far between as compared 'with the number of such lines in the 
higher regions. Of course the resolution of the spot-apectrum into 
Lines tends to indicate that the absorption which darkens the centre 
of a sun-spot is produced, not by granules of solid or liquid matter, 
but by matter in the gaseous form ; and it becomes interesting to 
inquire what substances are capable of producing such a spectrum, 
and under what conditions. As to the fineness and number of the 
lines, it may be noted that in the region included between b x and 6 4 
