Movement 406
AnimatedOriginal 

406. Mechanical means of describing parabolas, the base, altitude, focus, and directrix being given. Lay straight edge with near side coinciding with directrix, and square with stock against the same, so that the blade is parallel with the axis, and proceed with pencil in bight of thread, as in the preceding.

免费欧洲美女牲交视频_免费人成在线观看网站_免费岛国片在线观看x片喷水