Already, however, the general scheme was clear. The ice caps were far larger than those believed to have existed on Earth during the Pleistocene Ice Age, stretching in some places to within twenty (Earth) degrees of the equator. Most of the seas around the equatorial belt were completely locked in by coastlines and ice. An assortment of dots and symbols scattered across the land masses in the ice-free belt and, more thinly, over the ice sheets themselves, seemed to indicate towns and cities.

When Hunt received an invitation to come up and have a look at the maps, the scientists working on them showed him the scales of distance that were printed at the edges. If they could only find some way of converting those numbers into miles, they would have the diameter of the planet. But nobody had told them about the tables the mathematics section thought might be mass-unit conversion factors. Maybe one of the other tables did the same thing for units of length and distance? If so, and if they could find a reference to Charlie's height among his papers, the simple process of measuring him would allow them to work out how many Earth meters there were in a Lunarian mile. Since they already had a figure for the planet's surface gravity, its mass and mean density should follow immediately."

This was all very exciting, but all it proved was that a world had existed. It did not prove that Charlie and the Lunarians originated there. After all, the fact that a man carries a London street map in his pocket doesn't prove him to be a Londoner. So the work of relating numbers derived from physical measurements of Charlie's body to the numbers on the maps and in the tables could turn out to be based on a huge fallacy. If the diary came from the world shown on the maps but Charlie came from somewhere else, then the system of measurement deduced from the maps and tables in the diary might be a totally different system from the one used to record his personal characteristics in his papers, since the latter system would be the system used in the somewhere else, not in the world depicted on the maps. It all got very confusing.