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82. As the surface of an oblique prism is often found to be more difficult of development by the student draughtsman than that of a right one, the next problem will show how it may be correctly found. 190 FIRST PRINCIPLES OF Fiy. 192 LIECHANICAL AND ENGINEERING DRAWING 191 Problem 88 (Fig. 192). Given the side elevation of an oblique prism ; to find the development of its surface. . Let abed, No. 1, Fig. 192, be the given elevation of the prism, with its end c d resting on a horizontal plane. In this position, it is evident that. an ordinary front elevation of it, as of that of the frustum in No. 2, Fig. 191, would be of no service in this case, as the bounding edges of its sides, being inclined to the horizontal, would not give actual but only apparent lengths in projection. To find the actual sizes of all the sides and ends of the solid, and their relative position to each other, on a flat surface, a view directly at right angles to one of the sides of the prism is necessary. Now this view may be found in two ways. The prism may be turned on its horizontal edge at c, as on a hinge, until its inclined edge a c becomes vertical as shown in dotted lines and its development found when so posed. Or, it may be found at once from the prism in its inclined position, with less chances of error, by a projection of its bounding surfaces, taken when looked at in the direction of the arrow x ; such a view being tantamount to assuming the IL of the plane of projection to be drawn through c, at right angles to the edge c a of the prism, and its surface laid out flat on the VP. To find the develop-