Mathematica 2.1 for MS-DOS 386 (Student Version)     
Copyright 1988-92 Wolfram Research, Inc.

In[1]:= << oogl.m

In[2]:= s1 = Plot3D[ x y (x^2 - y^2)/(x^2 + y^2),
        {x, -2, 2}, {y, -2, 2},
        PlotPoints -> 30]

In[3]:= c1 = Show[ContourGraphics[s1], ContourShading -> False]

In[4]:= g1 = First[Graphics[c1]]

In[5]:= g1 =
        Graphics3D[g1 /. Line[x_] :>
        Line[ Map[ Append[#, -2]&, x]]]

In[6]:= Show[s1, g1, ViewPoint -> {1.3, -2.4, 1}]

In[7]:= WriteChunk["mychunk2", %]