!   G. Cowan,  Exercises in Statistical Data Analysis
!
!   Data from Jean Perrin on the number of mastic particles observed
!   at different heights in a water emulsion.  The first measurement
!   is arbitrarily assigned a height of zero.
!
!   Sources: J. Perrin, "Mouvement Brownien et Realite Moleculaire", 
!   Ann. Chimie et Physique, 8eme serie, 18 (1909) 1-114;
!   "Les Atomes", Flammarion (1991), first edition 1913;
!   "Brownian Movement and Molecular Reality", in Mary-Jo Nye, ed., 
!   "The Question of the Atom", Tomash, Los Angeles, 1984.
!
!   Radius of particles = 0.52 microns
!   Density of mastic = 1.063 gm/cm^3
!
!   Height (microns)    Number of particles observed in a
!                       layer of approx. 1 micron depth
!
    0                   1880
    6                    940
   12                    530
   18                    305