  In 1827, Colladon carried out a series of experiments in Lac Leman (Lake
Geneva, Switzerland) to measure the speed of sound in water.
  The purpose of our contribution is to treat this measurement as an inverse
problem, and show, by theory how to solve the latter. It is thus revealed under
what circumstances it is legitimate to employ the time-of-flight scheme
underlying the Colladon experiments and how to bypass this scheme in order to
fully account for the temporal and geometric characteristics of the source (of
sound), the temporal characteristics of the received signal and the error
incurred by the finite distance between the source and receiver.
