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112 FIRST PRINCIPLES OF MECHANICAL AND ENGINEERING DRAWING 113 the student a fuller insight into the methods of procedure in such a case, is the one adopted. Now, as the cylinder is shown as vertical and the section plane inclined at 45 to its axis, to bring this plane perpendicular to the HP it must be moved through an angle of 45. For the purpose of the projection it is assumed that the upper part of the cylinder above, the section plane is removed. To bring the lower part into the required position it must be turned through a vertical arc of 45. To do this, at the point D in its base draw indefinitely to the right and left lines making angles of 45 with the IL. On the one to the right, set off Dp equal to DP ; and on that to the left, DC equal to DC the diameter of the base of the cylinder ; at c draw cs equal to CS, the long side of the cylinder, at right angles to cD ; join sp, then Dcsp will be the lower end of the cylinder when the plane of section SP is vertical, or at right angles to the YP and HP. The true form of the section can now be found. First draw in No. 2 the plan of the cylinder in its vertical position. Divide its diametral line AB into four equal parts in points 1, 2, 3 ; through these draw double ordinates and projectors to cut CD, No. 1, in 1, 2, 3. Transfer by arcs points 1, 2, 3 in CD, No. 1, to cD, and through these last draw lines parallel to cs to cut sp in points 114 FIRST PRINCIPLES OF 1', 2', 3'. For the form of the section sp draw in, in No. 3, the axial line a) a ; project over to it from sp, No. 1, the points s' and p, and