.C. His antecedents, the place and exact time of his birth and death,
are quite unknown. Neither are we quite certain as to the precise range
of his studies or the exact number of his discoveries. It appears that
he had a pupil named Hero, whose personality, unfortunately, is scarcely
less obscure than that of his master, but who wrote a book through which
the record of the master's inventions was preserved to posterity. Hero,
indeed, wrote several books, though only one of them has been preserved.
The ones that are lost bear the following suggestive titles: On
the Construction of Slings; On the Construction of Missiles; On the
Automaton; On the Method of Lifting Heavy Bodies; On the Dioptric
or Spying-tube. The work that remains is called Pneumatics, and so
interesting a work it is as to make us doubly regret the loss of its
companion volumes. Had these other books been preserved we should
doubtless have a clearer insight than is now possible into some at
least of the mechanical problems that exercised the minds of the ancient
philosophers. The book that remains is chiefly concerned, as its name
implies, with the study of gases, or, rather, with the study of a single
gas, this being, of course, the air. But it tells us also of certain
studies in the dynamics of water that are most interesting, and for the
historian of science most important.

Unfortunately, the pupil of Ctesibius, whatever his ingenuity, was a
man with a deficient sense of the ethics of science. He tells us in
his preface that the object of his book is to record some ingenious
discoveries of others, together with additional discoveries of his own,
but nowhere in the book itself does he give us the, slightest clew as to
where the line is drawn between the old and the new. Once, in discussing
the weight of water, he mentions the law of Archimedes regarding a
floating body, but this is the only case in which a scientific principle
is traced to its source or in which credit is given to any one for a
discovery. This is the more to be regretted because Hero has discussed
at some length the theories involved in the treatment of his subject.
This reticence on the part of Hero, combined with the fact that such
somewhat later writers as Pliny and Vitruvius do not mention Hero's
name, while they frequently mention the name of his master, Ctesibius,
has led modern critics to a somewhat sceptical attitude regarding the
position of Hero as an actual discoverer.

Th