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198 line which is the hypotenuse of a right triangle upon the base line E-1 and a finishing line upon base line 9–F.

The diagrams of triangles are now constructed by drawing short horizontal lines equal in length to their respective base lines with corresponding numbers and letters. Perpendiculars are erected at one end of each of these horizontals. Since the plane of the top of the transition is inclined, the altitudes of these triangles vary. This variation is shown in Fig. 278 where the altitudes of various triangles are plainly marked. In determining the altitude of any point it should be remembered that the altitude is always the perpendicular distance between the plane of the base and the point in question. These altitudes should be placed on the proper perpendiculars, and in this connection it may be noted that the altitude always changes with the number; that is, wherever the number 2 occurs the altitude of 2 as shown in Fig. 278 must be used. The hypotenuses of the several triangles are now drawn.

The pattern development is started by drawing a horizontal line equal in length to the side DA of Fig. 280. Upon this line the center point E should be placed. A perpendicular line is erected at point E equal in length to the hypotenuse of triangle E-1. This establishes point 1, and the distance from point A to point 1 should correspond exactly in length to the hypotenuse of triangle A-1.

Since the center line EF of Fig. 280 divides the figure into two equal parts the pattern can be developed on each side of line E-1 of Fig. 283 simultaneously. The experienced draftsman always takes advantage of this fact when a whole pattern is to be developed. The line D-1 in Fig. 283 is next drawn, and when a distance is laid off from point A a like distance is also laid off from point D. With point A as a center and a radius equal to the hypotenuse of triangle A-2 an arc is drawn bearing away from point 1. This is intersected by an arc drawn from point 1 with a radius equal to the distance 1-2 of Fig. 279. In like manner points 3, 4, and 5 are established, but it must be remembered that the distances between figures must be taken each time from the true section, Fig. 279. With point 5 as a center and a radius equal to the hypotenuse of triangle 5-B, an arc is drawn bearing away from point A. This is intersected by an arc drawn from point A with a radius equal to side A-B of Fig. 280. This establishes point B.

From B as a center and with the several hypotenuses of Group