94 SP. Langley— Minute structure of the Solar Photosphere. 
In the best definition I find that the normal darkness of the 
outer penumbra is nothing else than the darkness of the gray 
medium in which the granules float all over the sun, though 
much deeper tints are here and there found, which sometimes 
make the penumbra almost resolvable into a ring of little spots. 
Over this shade stretch bere and there bright filaments, which 
are continuous with the granules of the photosphere (Kg. I’; to 
E, and elsewhere), through it are sometimes dimly traceable fila 
ments which apparently float at lower depths. It seems to me 
that there is no room for doubt, that “filaments” and “granules” 
. 
definition during which such work: can be carried on, to so 
vals which separate them are not less than ’’3. The sum of 
