scooped out some of the rubbish--the crevice was so narrow that it barely
admitted his arm--and finally dug a hole with his fingers fully fourteen
inches deep, revealing an egg, pink with freshness.

A more unlikely spot for a scrub fowl to lay, could hardly be imagined.
There was no mound, the crevice being merely filled flush, and the
vegetable rubbish packed between the flat rocks did not appear to be
sufficient in quantity to generate in its decay the temperature necessary
to bring about incubation. Yet the egg was warm, and upon reflecting that
the sun's rays keep the granite slabs in the locality hot during the day,
so hot, indeed, that there is no sitting down on them with comfort, I
perceived that here was evidence on which to maintain an argument of rare
sagacity on the part of the bird, and that the hypothesis might be thus
stated: This cool-footed cultivator of the jungle floor had during the
casual rambling on sunlit spaces become conscious of the heat of the
rocks. Being impressed, she surveyed the locality, and of her deliberate
purpose selected a spot for the completion of her next ensuing maternal
duties which, while it scandalised the traditions of her tribe, presented
unrealised facilities.

This was a natural incubator, certainly, but superior to those in common
use in that the solar heat stored by the stone during the day rendered
superfluous any large accumulation of vegetable matter. Surely it is but
a short and easy step from the perception of solar heat to the conception
that such heat would assist in the incubation of eggs. None but a
mound-builder who, of course, must have general knowledge on the subject
of temperatures and the maintenance thereof, could conceive that these
heated rocks would obviate the labour of raking together a mass of
rubbish. Further, her inherent perception that moist heat due to the
fermentation was vital towards the fulfilment of her hopes of posterity