SCIENTIFIC SUMMARY. 
425 
as to its existence; and the tardiness with which it was observed may 
perhaps be accounted for by the fact that attention was principally directed 
to an examination of the dark or partially opaque details of the photographs 
which correspond to the luminous details of the corona, whereas this was a 
bright or transparent structure; and bright spots, lines, or patches had 
always been regarded as photographic defects, and consequently but little 
attention had been paid to them. The original negatives are very small : 
the dark moon is represented by a transparent circle about —ths of an inch 
in diameter, and the whole extension of the corona could be covered by a 
sixpence. The separate details of the coronal structure are therefore very 
minute, and it would be impossible from the examination of a single 
negative to determine whether any small marking has its origin in some 
almost microscopic impurity on the collodion, or whether it represents a 
vast mass of many million cubic miles in the corona : it is only by a careful 
comparison of the different negatives that such photographic flaws can be 
properly eliminated. For this purpose a catalogue has been made, contain- 
ing a list of the negatives upon which each detail can be distinguished, and 
the details entered in the catalogue have also been drawn. In this work I 
have been fortunate enough to be aided by a most accurate and conscientious 
artist (Mr. Wesley), for whose laborious perseverance in the task I 
cannot be too thankful. 
“ While working at a group of coronal structure on the eastern equatorial 
limb, Mr. Wesley noticed that a small bright spot, or flaw as we then 
considered it, occupied apparently the same position in negatives 1 and 4 of 
Lord Lindsay’s series. On examining the others of Lord Lindsay’s or the 
Baikul series, we found that a bright spot or flaw was more or less distinctly 
to be traced in the same place on all of them. I at first thought that it must 
be due to a star seen through the corona, but a little reflection showed us 
that this explanation could not be sustained, for the image of a star would 
have been represented by a dark or very opaque point, whereas this was 
bright ; and therefore the collodion had at this point been less acted upon 
than by the light from the surrounding details. On a closer examination of 
the plates upon the next fine day, three partially transparent circular arcs, 
concentric with the bright spot, were detected above it. The middle one of 
the three arcs is the most distinct, and can be traced without any doubt 
upon four out of the five Baikul negatives. 
u At this time I had only Lord Lindsay’s negatives and two enlarged 
copies of the Java photographs to which I could refer. As all traces of the 
structure were lost on the copies of Lord Lindsay’s negatives, I was not 
surprised to find that it could not be seen on the Java enlargements. After 
a short time I obtained the loan of Colonel Tennant’s original negatives 
from Mr. De La Hue. They were taken at Ootacamund, a distance of more 
than 120 miles from Baikul, and I was therefore not a little astonished and 
pleased to find that the central bright spot was traceable on five out of the 
six negatives of his series. The central arc was just traceable on four out 
of the six negatives, and the inner arc is to be made out on three of the 
negatives. 
“No difference can be detected in the position of the central spot and 
concentric arcs relatively to the details of the corona in passing from the 
