array bug

lines 1123 - 1126 in should be changed at c = C[i,j] to the
following. As it now stands a floating point number from a numeric array
will generally register as type array rather than type float and be
rejected as not iterable when later tested.

        for i in range(Nx-1):
            for j in range(Ny-1):

    c = C[i][j]