Logarithmic Spiral Curve French Curves Small 320×236 Medium 640×473 Large 1024×756 Download Tiff Original 2400×1773 | (166.5 KB) Description A Logarithmic Spiral French curve, or irregular curve, is used to draw short elliptical radius curves by using points. The log curve is approximately closely shaped to a cycloid and other mathematical curves. Keywords curve ruler, curve rulers, curved ruler, log curve ruler, Logarithmic Curve French Curves, Logarithmic Curve Irregular Curve, Ruler, rulers Galleries Mechanical Drawing Tools Source: French, Thomas E A Manual of Engineering Drawing for Students and Draftsmen (New York, NY: McGraw-Hill, 1911)