Solar Structure with Observation. 197 
observed not in an isolated instance, but as a general charac- 
teristic of the solar surface, whose features are thus again 
assimilated to atmospheric ones in some degree like our own. 
rom the preceding facts of observation, it appears that the 
a 
must, if it exist, be at a distance, below the surface of the pho- 
tosphere, considerable even with reference to the dimensions we 
here deal with. 
(2.) It seems difficult to reconcile the bright, sharply-defined 
inner penumbral edge, and the regular structure discerned in 
the umbra, with another view, in which this umbra is a sort of 
stagnant pool, formed by cold vapors, or clouds, which have 
than with the views peculiar to Father Seech 
(8.) Finally, it seems to be little more than a summary of the 
facts of observation already rehearsed, to say that traces of a 
vortical action are found throughout the spot, and especially in 
the umbra. e theory which regards cyclonic or vortical 
action as @ prominent agent in determining the forms we have 
studied, appears then to be in closer accordance with observa- 
tion than the former. 
As the substance of the present article was written before 
Father Secchi’s remarks appeared in the August Memorie, it 
was originally prepared without reference to the questions 
raised there, and without any special reference to the cyclonic 
theory; and it is in no sense meant as a complete expression of 
opinion on those several points, in connection with which 
Father Secchi has done me the honor to cite my name. As one 
of the few who have used an instrument of adequate power in 
the particular field of research in which a large part of his 
labors have lain, I am more able than most, perhaps, to appre- 
ciate his eminent qualities as an observer. When, however, he 
states that longer study of the sun than I have yet given, will 
* . . . “Tl solo errore dell ‘illustre osservatore (i. e., Herschel) fu di estendere 
la massa oscura su tutto il globo sotto la fotosfera, mentre in non forma 
che pezze 0 chiazze assai limitate—P. Secchi, Memorie, Agosto, 1874. 
