  We compare the option pricing formulas of Louis Bachelier and
Black-Merton-Scholes and observe -- theoretically as well as for Bachelier's
original data -- that the prices coincide very well. We illustrate Louis
Bachelier's efforts to obtain applicable formulas for option pricing in
pre-computer time. Furthermore we explain -- by simple methods from chaos
expansion -- why Bachelier's model yields good short-time approximations of
prices and volatilities.
