  The Italian astronomer Giovanni Battista Riccioli is commonly credited with
performing the first precise experiments to determine the acceleration of a
freely falling body. Riccioli has been discussed by historians of science,
sometimes positively but often not, but translations of his work into modern
languages are not readily available. Presented here is a translation of his
experiments regarding the nature of the motion of a falling body. Riccioli
provides a thorough description of his experiments, and his data are quite
good. He appears to have a model approach to science: He attacks the question
of free fall with the expectation of disproving Galileo's ideas, yet he is
convinced by his data that Galileo is indeed correct, and he promptly informs a
former prot\'eg\'ee of Galileo's of the results.
