50S 
ON DRAWING CRYSTALS, &C. 
C D, in dotted lines ; to express lines drawn upon the sur- 
face of forms in interrupted lines E F ; and lines in their 
interior by alternating dots and short lines, like G H. 
Very often it occurs, particularly with beginners, who 
are not yet accustomed to judge rightly of the probable 
size of a form, to be obtained by several successive pro- 
cesses, that the result is either smaller or larger than is 
wished for, and a method is therefore desirable for enlar- 
ging or reducing it to a more convenient size. Draw to this 
end from any determined point, within or without the 
figure, towards every solid angle of the figure, a straight line, 
and take respectively equal parts of the whole upon these; the 
points determined will be the analogous points of the new 
figure. If, for instance, the hexahedron A F (Fig. 17.) is so 
much to be reduced, that the edge of the new figure becomes 
equal to two-fifths of the edge of the original, it will be 
necessary to draw N A, N B, N C, N D, &c. and to take 
upon these lines N A^ =: f N A, N = | N B, N 
zi I N C, N = I N D, &c. The hexahedron is now 
completed by joining these points by the straight lines 
A^ B^ B^ T>\ CS C A^ &c. In most cases, however, 
it will be more expeditious to draw the axes, like AF, BE, 
&c., or other lines, through the centre of the solid, and 
take upon these the same relative distances A^^ M =: | A M, 
&c., which will likewise yield a hexahedron, the side of 
which is equal to two-fifths of the side of the original form. 
