20.Make an upright parallelopiped. (fig. 16.)
When the bases of the prism are parallelograms, the body is called a parallelopiped. All the six faces are then parallelograms, and the two opposite faces are equal.
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21.Make an oblique parallelopiped. (fig. 17.)
22.Make a Cube. (fig. 18.)
The cube is a parallelopiped, all of whose faces are equal squares, and each placed at right angles with the contiguous or next squares.
A cube is a solid square, but it will be perceived, that in consequence of perspective, only the front and back faces appear square. These two faces should be traced first, and the rest will easily be added. Dice are cubes.
23.Draw an oblique cube. (fig. 17. if you make its sides equal.)
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24.Cut a prism by a plane parallel to its bases. (fig. 19.)
