  Artificially produced chemical elements heavier than uranium have been known
for more than seventy years and the number of superheavy elements continues to
grow. Presently 26 transuranic elements are known. This paper examines the
earliest scientific interest in the very heavy elements and the related
question of an upper limit of the periodic system. In the period from the 1880s
to the early 1930s, three kinds of questions appealed to a minority of
physicists, chemists and astronomers: (1) Why is uranium the heaviest known
element? (2) Do there exist transuranic or superheavy elements elsewhere in the
universe, such as in stellar interiors? (3) Is there a maximum number of
elements, corresponding to a theoretical limit for the periodic system? The
early attempts to answer or clarify these questions lacked a foundation in
nuclear physics, not to mention the total lack of experimental evidence, which
explains why most of them were of a speculative nature. Although the
speculations led no nothing, they are interesting in their own right and
deserve a place in the history of the physical sciences.
