INTENSITY OE CORONAL LIGHT DURING THE SOLAR ECLIPSE OF 1893. 441 
identical in character with that already given ( loc . cit., p. 380), showing, as formerly 
stated, that the diminution in intensity from the moon’s limb outwards is less rapid 
than that demanded by the law of inverse squares. 
The results are as follows :— 
Distances in solar 
semi-diameters. 
Photometric intensity. 
Obse 
1893. 
rved. 
1886. 
Law of 
inverse squares. 
1-6 
0-060 
0-066 
0-066 
2-0 
0-048 
0-053 
0-042 
2-4 
0-038 
0-043 
0-029 
2-8 
0-030 
0 034 
0-022 
3-2 
0-024 
0-026 
0-016 
3-4 
0-018 
0021 
0-013 
These numbers would appear to show that the actual brightness of the corona was 
probably not very dissimilar at the two eclipses, the slight apparent diminution 
observed during the 1893 eclipse being, in all probability, due to the haze or 
opalescence in the air which, as already stated, prevailed at the time. This haze, 
caused more by suspended and finely-divided solid matter than by precipitated 
moisture, undoubtedly contributed to the general sky-illumination at the time of 
totality. The actual gloom during this phase of the eclipse at Fundium was 
certainly much less than at Grenada in 1886. It must not, however, be forgotten 
that the altitude of the sun was very different on the two occasions. At Grenada it 
was only about 19°; the amount of cloud was from 7 to 8 (overcast = 10) at the 
time of totality ; and much of it was in the neighbourhood of the sun ; whereas at 
Fundium the sun’s altitude was 52° and the sky was of a bluish-grey colour and 
practically free from cloud. 
The effect of these different conditions in the sky in the neighbourhood of the disc 
is seen in Mr. Forbes’s measurements when compared with those of Lieutenant 
Douglas at Grenada. The ten fairly concordant observations at Fundium give an 
average value of 0'026 Siemens unit at one foot from the screen ; the highest and 
probably the most accurate value observed by Lieutenant Douglas fifteen seconds 
after totality, with the same photometer, although with a different lamp and 
galvanometer, was (P0197. 
The observations are not sufficiently precise to enable any valid comparison to be 
made between the brightness of the corona at the poles and at the equator, nor are 
they numerous enough to make it worth while to attempt to seek for the law 
MDCCCXOYI. — A. 3 L 
