Page:Logic Taught by Love.djvu/34

30 lighted night-light in the bottom of a tall jar, and throwing the shadow of the rim of the jar on surfaces held in different positions.

The best paper to use is that which is ruled in small squares (it can be procured at the shops which furnish educational apparatus). The paper may with advantage be laid on the table with its lines pointing to the cardinal points of the compass; so that a line of shadow can be described by stating, e.g., that it crosses so many squares from north to south, and so many from east to west.

Take a corkscrew-wire, with rings sufficiently large to throw a distinct shadow. It is possible to hold it so that its shadow is a mere circle; in another position it makes a mere wavy line. An ordinary spiral wire is easily procured, and in practice is sufficient; but we shall gain more instruction about the play of Natural forces if we picture to ourselves what would be the effect of using a spiral whose rings are elliptical. I shall assume here that we are using an elliptical spiral. The wire itself will then represent the path of a planet in space; one of its shadows pictures the path of the planet round its sun or suns; another, the path of the whirling storm-wind, to which Jesus compared that of Inspiration.

Let us now place our (elliptical) spiral in such a position that it casts no shadow except an ellipse, and, for convenience of reference, let us agree that the longer axis points north and south. Let us picture to ourselves a tribe of microscopic creatures, whose true destiny should be to proceed upwards in the direction of the coil as a whole, and who have a blind but irresistible impulse to do so. They have no mode of ascending