502 
ON DRAWING CllYSTALS 
droD, these lines will deteroiine the situation of the points 
Nj W^, and N^, N"^, in which the edges contiguous to 
one of the angles of the octahedron rise from the planes 
within which the hexahedron is contained. The part 
ANW N" N"i, situated beyond the face T U V V/ of the 
hexahedron, will therefore be cut oif by this face, and not 
appear in the combination at all. The same will be the case 
with all the other solid angles of the octahedron, and the 
combination itself will be contained under eight hexagons, 
the residue of the faces of the octahedron, and six squares, 
being the residue of the faces of the hexahedron. 
The same result may be obtained by a shorter process, 
thus : 
Project the figure of the octahedron, take AN^ = L 
n ' n ' 71 
and draw N", S S", W R", which are the intersections 
of the face A B L of the octahedron with the three adja- 
cent faces of the hexahedron. The same process applied 
to all the edges of the octahedron gives the intersections of 
all the faces of the two solids, which being expressed by 
straight lines, yield the projection of the combination 
wanted. 
Having obtained the figure of a double combination, it 
will be easy to add the faces of a third, then of a fourth 
simple form, and so on ; and here, as well as in the pro- 
jection of the simple forms themselves, we may often take 
advantage of many circumstances, which will offer them- 
selves to our attention in the practical attempt of laying 
down the representations of crystals, in the proportion of 
our actual information in regard to the various departments 
of crystallography. 
