384 
ME. WAEEEN DE LA EUE ON THE 
Table II. 
In Table II., columns 2, 3, and 4, is given a series of measurements from which are 
derived the versed sines of the sun and moon, and in columns 7 and 8 other measure- 
ments from which are obtained the lengths of the chord joining the cusps given in 
column 9. Columns II and 12 the resulting semidiameters of the moon and sun 
respectively, calculated upon these data. On account of the change in the apparent 
diameter of the moon during the eclipse, the measures in column II are not adapted 
for giving a mean result of the whole series ; but the case is different for the sun, and 
hence the average of the measures of column 12 has been taken out for comparison 
with the mean semidiameter obtained by direct measurement ; the mean semidiameter 
of the sun given by Table II. is 1903T thousandths of an inch, which differs by only 
— 1-91 thousandths = — 0"'9 from the value given in Table I. With respect to the 
moon’s radius, it should be borne in mind that the photographs near the commencement 
and the end of the eclipse are not well adapted for such calculations, as a very minute 
error in measuring the chord or the versed sine introduces a great error in the resulting 
calculated semidiameter ; and any rounding off or indistinctness of the cusps, especially 
near the epochs of commencement and end, militates greatly against exact determinations 
of the moon’s radius by the method employed. For these reasons, it has been necessary 
to omit certain numbers of column II, in deducing the averages for the moon’s semi- 
diameter, namely. Nos. 7, 10, 14 , 39, 41, 42, and 43: by bringing together into three 
groups the remaining calculated semidiameters of the moon, we obtain for the mean 
epochs of these groups the following results, as compared with those deduced from 
Mr. Faeley’s numbers for the same epochs. 
Mean 
epoch, 2*' I?”. 
Mean epoch, 3'‘ I”. 
Mean epoch. S'* 34“ 
, . (De La Eue . 
993-8 
993-3 
990-9 
Moons radius<T^ 
(Faeley . . 
994-1 
992-9 
991-9 
Difference - 
- 0-3 
+ 0-4 
- 1-0 
These numbers are remarkably near the computed numbers, and render manifest that 
even so minute a change as the decrease in the moon’s semidiameter dming the eclipse 
is traceable in the photographs. Taking the differences of semidiameter at the first and 
last epochs, the augmentation of the moon’s radius becomes more apparent, and not far 
from the true numbers ; thus 
Moon’s semidiameter. 
De La Eue. 
Earley. 
h m 
It 
At 
. . 2 17 
993-8 
994-1 
At 
. . 3 34 
990-9 
991-9 
Difference 
. . 2-9 
2-2 
