48 
IOWA ACADEMY OF SCIENCE Vor. XXIX, 1922 
might be urged that the universe has no plural and that to think 
of island universes is to fall into the old fallacy of Euclidian 
space. But Einstein shows that in the Euclidian universe the aver- 
age. density of matter is necessarily zero. Interpreting then, the 
structure of the universe by the general theory of relativity, all the 
difficulties of the Newtonian theory are overcome, leaving us free 
to indulge in a world picture as unbounded as we please, yet com- 
plete and finite. There is no danger that it will ever become 
destroyed, because no energy or matter can dissipate into infinity 
since space is not infinite. The infinity of the cosmos is thus re- 
jected without arbitrary setting of boundaries. As Schleck in 
a bit of ecstacy phrases it: “By combination of physical, mathe- 
matical and philosophic thought, genius has made it possible to 
answer by means of exact methods questions concerning the uni- 
verse which seemed doomed forever to remain the objects of 
vague speculation.” 
The Observatory, 
Drake University. 
