DEFLECTION OF LIGHT——-DYSON AND OTHERS. 158 
Taste VIII.—Comparison of the Eclipse and comparison photographs, etc.—Con. 
COMPARISON PLATES, DECLINATION. 
Betas elaine atin <)sie~i= —0. 07 +0. 08 —0. 26 —0. 04 —0, 26 —0.18 —0. 16 —0. 13 
De sena ne osteecee ase. — .23 — .03 + .03 -00 Sig + .03 — .20 — .08 
Bmeepeerisi oP eis 7/2 = a + .23 + .05 + .29 +..18 + .45 + .53 + .23 + .28 
Seat ose Ree oe + .64 + .41 +,.42 + .36 + .48 + .60 + 204 =>) 249 
Pasencat se teeckeeaaass + .22 + .36 + .33 + .26 + .41 + .21 + .32 + .30 
1 A oa Maen + .28 + .32 + .31 + .36 + .36 + .15 + .29 + .30 
Po bsncerposcnasae eee + .25 +) e/14 + .18 + .21 + .09 — .03 + add + .16 
Subtracting the results of the comparison plates so as to eliminate 
the errors arising from the intermediary scale plate we find for the 
displacements of the different stars, as compared with those as given 
by Einstein’s theory, with value 1.75’’ at the sun’s limb: 
Displacement in right Displacement in 
ascension. declination. 
No. of star. eee 
Observed. | Calculated.| Observed. | Calculated. 
ur au wt ve 
DEST SECE 234 —0;19 —0.32 +0. 16 +0. 02 
Shae sides — .29 — .31 — .46 — .43 
Bee h ae scasee — .ll — .10 + .83 arate! 
Seee's ese — .20 — .12 +1. 00 45 d2y 
(ese ae as — .10 + .04 + .57 + .40 
DOLE Bae — .08 + .09 + .35 + .32 
Dette eee oe + .95 + .85 — .27 — .09 
{The sign of the displacement in right ascension of No. 6 was printed in Philosophical 
Transactions of the Royal Society of London as +. This and several other typographi- 
eal errors, kindly pointed out by Prof. Bauer, have been corrected.] 
PHOTOGRAPHS TAKEN WITH THE ASTROGRAPHIC OBJECT GLASS. 
23. As stated above, these photographs were taken with the astro- 
graphic object glass stopped down to 8 inches, mounted in a steel 
tube and fed by a 16-inch celostat. From many years’ experience 
with the object glass at Greenwich it is certain that when the object 
glass is mounted in a steel tube the change of scale over a range of 
temperature of 10° F. should be insignificant, and the definition 
should be very good. It was realized that this high standard would 
not be obtained with the glass used in conjunction with the ccelostat 
taken to Brazil, but nevertheless the results shown when the plates 
were developed were very disappointing. The images were diffused 
and apparently out of focus, although on the night of May 27 the 
focus was good. Worse still, this change was temporary, for with- 
6 The following note made at the time is quoted in full: ‘“‘ May 30, 3 a. m., four of the 
astrographic plates were developed, and when dry examined. It was found that there had 
been a serious change of focus, so that, while the stars were shown, the definition was 
spoiled. This change of focus can only be attributed to the unequal expansion of the 
mirror through the sun’s heat. The readings of the focussing scale were checked next day, 
but were found unaltered at 11.0 millimeters. It seems doubtful whether much can be got 
from these plates,” 
