194 S..P. Langley— Comparison of certain Theories of 
retaining characteristics which show the type from which they 
have sprung. 
Attention was first directed to that dark interior, in which 
Dawes discerned still darker shades, which he called nuclei, as 
the unusual size of the spot and the irregularity of shade in the 
umbra seemed to favor their investigation. Aided by special 
optical devices, there became visible to close attention, forms 
which appeared to be affiliated to the better known ones of the 
penumbra, which were studied also, and a description of a part 
of whose characteristics, interesting perhaps in their bearing 
upon solar theories, follows 
a variety as to make classification difficult, the spiral type ue 
is an 
even of distinctly marked opposite flexures in the same fila- 
ments, show the complexity of the action which had been at 
work, 
(2.) An appearance which deserves remark is this. It has 
long since been observed that the interior border of the penum- 
(3.) In this connection we may best study the umbral forms 
