When Hunt talked to the mathematicians one afternoon, he was surprised to learn that they were unaware that the chemists and anatomists in other departments had computed estimates of surface gravity. As soon as he mentioned the fact, everybody saw the significance at once. If the Lunarians had adopted the practice that was common on Earth—using the same units to express mass and weight on their own planet—then the numbers in the table gave Lunarian weights. Furthermore, there was available to them at least one object whose weight they could estimate accurately: Charlie himself. Thus, since they already had an estimate of surface gravity, they could easily approximate how much Charlie would have weighed in kilograms back home. Only one piece of information was missing for a solution to the whole problem: a factor to convert kilograms to Lunarian weight units. Then Hunt speculated that there could well be among Charlie's personal documents an identity card, a medical card—something that recorded his weight in his own units. If so, that one number would tell them all they needed to know. The discussion ended abruptly, with the head of the mathematics section departing in great haste and a state of considerable excitement to talk to the head of the linguistics section. Linguistics agreed to make a special note if anything like that turned up. So far nothing had.

Another small group, tucked away in offices in the top of Navcomms HQ building, was working on what was perhaps the most exciting discovery to come out of the books so far. Twenty pages, right at the end of the second book, showed a series of maps. They were all drawn to an apparently small scale, each one depicting extensive areas of the world's surface—but the world so depicted bore no resemblance to Earth. Oceans, continents, rivers, lakes, islands, and most other geographical features were easily distinguishable, but in no way could they be reconciled with Earth's surface, even allowing for the passage of fifty thousand years—which would have made little difference anyway, aside from the size of the polar ice caps.

Each map carried a rectangular grid of reference lines, similar to those of terrestrial latitude and longitude, with the lines spaced forty-eight units (decimal) apart. These numbers were presumed to denote units of Lunarian circular measure, since nobody could think of any other sensible way to dimension coordinates on the surface of a sphere. The fourth and seventh maps provided the key: the zero line of longitude to which all the other lines were referenced. The line to the east was tagged "528" and that to the west "48," showing that the full Lunarian circle was divided into 576 Lunarian degrees. The system was consistent with their duodecimal counting method and their convention of reading from right to left. The next step was to calculate the percentage of the planet's surface that each map represented and to fit them together to form the complete globe.