- DEFLECTION OF LIGHT—DYSON AND OTHERS. 175 
an amount much beyond the limits of its accidental error. For the 
reasons already described at length not much weight is attached to 
this determination. 
- It has been assumed that the displacement is inversely propor- 
tional to the distance from the sun’s center, since all theories agree on 
this,;\and, indeed, it seems clear from considerations of dimensions 
that a displacement, if due to gravitation, must follow this law. 
From the results with the 4-inch lens, some kind of test of the law is 
possible though it is necessarily only rough. The evidence is sum- 
marized in the following table and diagram, which show the radial 
displacement of the individual stars (mean from all the plates) 
plotted against the reciprocal of the distance from the center. The 
displacement according'to Einstein’s theory is indicated by the heavy 
line, according to the Newtonian law by the dotted line, and from 
these observations by the thin line, 
Radial displacement of individual stars. 
Caleula- Observa- 
Star. tion. tion. 
au LAA 
VW. p0 ses 0.32 0. 20. 
Ee ee 0.33 0. 32 
Goes 0. 40 0. 56 
PAS FREE 0.53 0.54 
APY CBee DERI ies 0,75 0. 84 
peg St ice 0. 85 0.97 
3.22.26... 0. 88 1.02 
Thus the results of the expeditions to Sobral and Principe can 
leave little doubt that a deflection of light takes place in the neighbor- 
hood of the sun and that it is of the amount demanded by Einstein’s 
generalized theory of relativity, as attributable to the sun’s gravita- 
6 
RADIAL DISPLACEMENT 
2 IN Oy 6 GS Om Ge Ow} 
é 
DISTANCE 90 60 50 49 30 25 
Fia. 2. 
