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OCR Rendition - approximate
v PATTERNS : THEIR OUTLINES AND CORES 7 7 parting or the eye occurs, whether it be the Inner or the Outer. At the bottom of Fig. 14, 49-54, is given a series of rings, spirals, and plaits, in which nearly all the clearly distinguishable varieties are included, no regard being paid to the direction of the twist or to the number of turns. 49 is a set of concentric circles, 5o of ellipses : they are rarely so in a strict sense throughout the pattern, usually breaking away into a more or less spiriform arrangement as in 51. A curious optical effect is connected with the circular forms, which becomes almost annoying when many specimens are examined in succession. They seem to be cones standing bodily out from the paper. This singular appearance becomes still more marked when they are viewed with only one eye ; no stereoscopic guidance then correcting the illusion of their being contour lines. Another curious effect is seen in 53, which has the appearance of a plait or overlap ; two systems of ridges that roll together, end bluntly, the end of the one system running right into a hollow curve of the other, and there stopping short ; it seems, at the first glance, to run beneath it, as if it were a plait. This mode of ending forms a singular contrast to that shown in 51 and 52, where the ridges twist themselves into a point. 54 is a deep spiral, sometimes having a large core filled with upright and nearly parallel lines ; occasionally they are bulbous, and resemble the commoner " monkey " type, see 35. When the direction of twist is described, the
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