330 Dr. Brinkley's observations for investigating 
before. Had 20^'' been used for the constant of aberration, 
the result would have been only less by half a second than 
before. 
In fact, the quantity of discordance does not differ from 
what I had before observed, but part of it now appears to 
arise from the constant of aberration being greater ; a con- 
clusion that will be deemed very important, should it be con- 
firmed by future observations or other instruments. The 
parallax of Arcturus is somewhat less than before, and that of 
a. Cygni considerably less, y Draconis, as before, exhibits no 
parallax; the small negative result of of a second may 
safely be referred to the unavoidable errors of observation. 
The new results agree with the former, in showing that the 
Pole Star has no sensible parallax. 
With respect to the constant of aberration, it is almost un- 
necessary to remark its important bearing on the theory of 
light. Should a decided difference in the quantity of that 
constant, for two stars, be established, it would be decisive 
against the undulatory system ; and it would also show, 
that the corpuscular theory could not, without the addition 
of principles at present unknown, explain the phenomena 
of light. I trust the results here obtained will be found 
to possess some interest, and may induce others to pursue 
the same object. I dare not venture to draw any con- 
clusion from them relative to these important points. The 
two stars v\ Ursas Majoris and y Draconis appear to point out 
a difference. These stars, by their proximity to the zenith 
and other circumstances, are well adapted for obtaining ex- 
act results. The observations of each star seem to be very 
