"Of course! If my theory is correct, the shifting is due to them."
"Explain!"
"So far as I can. But here I am only on surmise, or theory pure and simple. I may be all wrong, or I may be right—I shall know more before I am done with Shleenanaher. My theory is that the shifting is due to the change in the beds of clay, as for instance by rains washing them by degrees to lower levels—this is notably the case in that high clay bank just opposite the Snake's Pass. The rocks are fixed, and so the clay becomes massed in banks between them, perhaps aided in the first instance by trees falling across the chasm or opening. But then the perpetually accumulating water from the spring has to find a way of escape; and as it cannot cut through the rock it rises to the earth bed, till it either tops the bed of clay which confines it or finds a gap or fissure through which it can escape. In either case it makes a perpetually deepening channel for itself, for the soft clay yields little by little to the stream passing over it, and so the surface of the outer level falls, and the water escapes, to perhaps find new reservoirs ready made to receive it, and a similar process as before takes place."
"Then the bog extends and the extended part takes the place of the old bog which gradually drains."
"Just so! but such would of course depend on the level; there might be two or more reservoirs, each with a deep bottom of its own and united only near the
