Before going further, let us halt a moment and glance around. As we hinted at the outset of this study, it would be idle to attempt to derive every comic effect from one simple formula. The formula exists well enough in a certain sense, but its development does not follow a straightforward course. What I mean is that the process of deduction ought from time to time to stop and study certain culminating effects, and that these effects each appear as models round which new effects resembling them take their places in a circle. These latter are not deductions from the formula, but are comic through their relationship with those that are. To quote Pascal again, I see no objection, at this stage, to defining the process by the curve which that geometrician studied under the name of roulette or cycloid,--the curve traced by a point in the circumference of a wheel when the carriage is advancing in a straight line: this point turns like the wheel, though it advances like the carriage. Or else we might think of an immense avenue such as are to be seen in the forest of Fontainebleau, with crosses at intervals to indicate the cross-ways: at each of these we shall walk round the cross, explore for a while the paths that open out before us, and then return to our original course. Now, we have just reached one of these mental crossways. Something mechanical encrusted on the living, will represent a cross at which we must halt, a central image from which the imagination branches off in different directions. What are these directions? There appear to be three main ones. We will follow them one after the other, and then continue our onward course.