Adjoining the Memorial Grotto lay the Cartographic Scroll hall—a spacious, dry gallery carved from stone-hard boxwood, lined with thousands of shallow pigeonholes containing tube-shaped cases of cured birch-bark and stone-hard slate rolls.
In the center of the writing hall stood a massive drafting table ten paces long, hewn from a single slab of black dark rock that had been ground flat to within a fraction of a tiny fraction of an inch. Suspended above the table were three oil-lamps burning refined pine-pitch, casting a brilliant, shadowless white light across the drafting surface.
Here, for three hours, Qiao Ming and Yan Zhiqiu worked alongside the four master scribes of the clan to achieve what no royal land-mapper had ever accomplished. The synthesis of surface trigonometry and deep-root sound sonar into a single, unified ball-shaped atlas.
Yan Zhiqiu laid the Broken Slate upon the center of the dark rock table. Beside it, Qiao Ming placed his black slate ledgers, filled with the thousands of soundings, air-pressure readings, tension metrics, and lead-line tallies he had recorded since their plunge from the Grand Round hall.
Across the table, the elder scribes unrolled a huge sheet of cured thick parchment four yards long, prepared from the inner bark of a stone-hard Dawn-Redwood. Upon this surface was drawn the Master Acoustic Chart of the twelve roots, recording every cave, gallery, drain tube, and burl across eighty entry halls.
