Sir John Lubbock’s Address. 849 
then, in another three and a half hours, reassumes its original 
brilliancy. These changes seem certainly to indicate the pres 
ence of an opaque body, which intercepts at regular intervals 
a part of the light emitted by Algol. 
Thus the floor of heaven is not only “thick inlaid with 
patines of bright gold,” but studded also with extinct stars; 
once probably as brilliant as our own sun, but now dead an 
cold, as Helmholtz tells us that our sun itself will be, some sev- 
enteen millions of years hence. 
two largest telescopes in the world should both be Irish. 
he general result of astronomical researches has been thus 
eloquently summed up by Proctor:—“ The sidereal system is 
altogether more complicated and more varied in structure than 
has hitherto been supposed ; in the same region of the stellar 
epths coéxist stars of many orders of real magnitude; all 
orders of nebule, gaseous or stellar planetary, ring-formed, 
elliptical, and spiral, exist within the limits of the galaxy; and 
lastly, the whole system is alive with movements, the laws of 
which may one day be recognized, though at present they 
appear too complex to be understood.” 
e can, I think, scarcely claim the establishment of the 
undulatory theory of light as falling within the last fifty years; 
for though Brewster, in his “ Report on Optics,” published in 
our first volume, treats the question as open, and expresses 
himself still unconvinced, he was, I believe, almost alone in his 
preference for the emission theory. The phenomena of inter- 
ference, in fact, left hardly any —if any —room for doubt, 
and the subject was finally set at rest by Foucault’s celebrated 
