usd downloader 1.3.5.1

and through the points of division draw in the meridians on the frustum. Next produce its base line b c indefinitely, and set off on it from c, the eight equal parts into which the semi-circle on be is divided. Through the points of division, draw lines parallel to the sides of the MECHANICAL AND ENGINEERING DRAWING 201 frustum, and number them as shown. Then from each of the points in the line ad, where the meridians drawn on the front side of the frustum intersect it, draw projectors parallel to b c produced, to cut its corre- sponding meridian in No. 3. A line drawn through the points of intersection of the projectors and meridians, will then give the develop- ment of the front half of the frustum. For the back half, produce the projectors drawn through the points 1 to 7 in ad, to cut the corresponding meridians on the back face of the frustum ; then a line drawn through their intersections as shown in No. 2, will give the development of the top edge of the frustum. For the side and bottom edges, draw in, in full, the lines d c, d'c, c c, and the required development is complete. 90. As parts of the surface of an oblique cylinder sometimes enter into the design of boiler flues, uptakes, air shafts, etc., it is necessary that the difference between its development and that of a right cylinder should be understood by the student. The particular difference between the two solids, the right and the oblique cylinder, is, that in the former its axis is perpendicular to its bases or ends ; whereas in the latter it is inclined to them ; the ends in both cases being circular and parallel to each other. There is, however, another important difference, which affects their developments ; viz., that a section of either, taken parallel to its ends, is a circle; while a