  The discovery of cosmic rays, a milestone in science, comprised scientists in
Europe and the US and took place during a period characterised by nationalism
and lack of communication. Many scientists that took part in this research a
century ago were intrigued by the penetrating radiation and tried to understand
the origin of it. Several important contributions to the discovery of the
origin of cosmic rays have been forgotten and in particular that of Domenico
Pacini, who in June 1911 demonstrated by studying the decrease of radioactivity
with an electroscope immersed in water that cosmic rays could not come from the
crust of the Earth. Several historical, political and personal facts might have
contributed to the substantial disappearance of Pacini from the history of
science.
