TayLtor—On the Photographing of the Solar Corona. 275 
An examination of my photographs taken in Brazil shows 
that there is a steady increase in the extension of the corona on 
the plates of the first series, in which the photographic actions 
increased from ‘088 to 6°666, although the latter suffered slightly 
from sky fog; but in the second series there is a steady increase up 
to 20 seconds, and practically no gain is shown by the 50, 120, and 
150 seconds, while the two latter plates have suffered very much 
from sky fog, and the inner portions of the corona are hopelessly 
burnt out. The best all round result for the inner and middle is 
obtained by a photographic action of less than 1, and there is a 
loss in external corona when the photographic action reaches 22. 
With Professor Schoeberle’s instruments a similar result is 
obtained. The 4:96-inch object-glass, of 46 feet focus, gives a 
photographic action of ‘0086 for 1 second exposure, and the photo- 
graphs taken with this instrument, in which the photographic 
action never reaches 1, are magnificent for the inner and middle 
corona, while they also show some portions of the external corona- 
With the 64-inch lens of 6 feet focus, the photographie actions 
were :— 
(1 second corresponds to a photographic action of *766.) 
Instantaneous, say = second, = ‘005 
lsecond = ‘766 
2 seconds = 1:°582 
A Mes B G4 
Se E18 
10 Ue ii 660 
16)" 29-256 
cy ron” 507; 
He finds the best picture of the external corona is given by 16 
seconds, corresponding to a photographic action of 12-256, a greater 
photographic action than this resulting in sky-fog and loss of 
detail in the external corona. The best photographie action found 
by Professor Schceberle falls between the English best (8-888) and 
the first English result in which loss by sky-fog is found, and 
indicates that an exposure of 29 or 380 seconds with the 4-inch 
lens of 60 inches focus is about the limit of good results. To go 
beyond this is to lose detail. 
