  We reexamine the the classical multidimensional scaling (MDS). We study some
special cases, in particular, the exact solution for the sub-space formed by
the 3 dimensional principal coordinates is derived. Also we give the extreme
case when the points are collinear. Some insight into the effect on the MDS
solution of the excluded eigenvalues (could be both positive as well as
negative) of the doubly centered matrix is provided. As an illustration, we
work through an example to understand the distortion in the MDS construction
with positive and negative eigenvalues.
